Cuckoo–hawk mimicry? An experimental test

We found clear differences in tit responses depending on the mounted species to which they were exposed. During the presentations of the two harmless controls, a familiar collared dove and a novel teal, the tits often continued to visit the feeders, and afterward their attendance returned to pre-exposure levels. By contrast, they avoided the feeders during and after both sparrowhawk and cuckoo presentations. The most striking result from experiment 1 was that the response was similar to sparrowhawks and cuckoos, even though cuckoos are of no threat to adult tits. 

The plumage manipulations in experiment 2 suggested that the strong alarm response to cuckoos depended on their resemblance to hawks because when their hawk-like underpart barring was obscured, the tits treated them as no more of a threat than doves. This supports the idea that the evolution of barring in parasitic cuckoos, revealed by the comparative analysis (Payne 1967; Kru¨ger et al. 2007), enhances their resemblance to hawks. 

However, underpart barring cannot be the only feature inducing an alarm response because the tits showed equally strong alarm to barred and unbarred hawks. Furthermore, little alarm was shown to barred doves. Therefore, the underpart barring must combine with other cuckoo features, for example, their grey upperparts and elongated wings and tail, to cause hawk resemblance. We found no significant effect of the specimen, which suggests that these results cannot be attributed to any peculiarities of the particular mounts we used. 

We also found no effect of the study site, so the tits on Wicken Fen, which would have experienced daily encounters with cuckoos during the previous summer, had equally strong responses to cuckoos as the tits in Cambridge and Madingley Wood, which were unlikely to have encountered cuckoos. This suggests that the strong effect of the cuckoo at both sites was not simply one of alarm to a novel stimulus. Tits attending rich food sources are especially vulnerable to attack because sparrowhawks learn that these are good locations for finding prey (Hinsley et al. 1995). 

Because sparrowhawks make surprise attacks (Newton 1986; Cresswell 1996), alarm to any hawk-like stimuli is likely to be adaptive, despite the loss of feeding time from frequent false alarms. Nevertheless, the 5 min exposure of the specimens gave the tits ample opportunity for close inspection, so it is remarkable that a cuckoo caused a strong alarm response, given that it lacks a hawk’s lethal weapons, namely talons and a hooked beak. If the inspection of a potentially dangerous predator is costly, then even a slight resemblance through shape, grey upperparts, and underpart barring may be sufficient to deter approach. 

Other studies have shown that mimics do not have to resemble the model perfectly to gain protection, especially when signal receivers regard the model as highly noxious or dangerous, or if the model is relatively common (Ruxton et al. 2004). Perhaps the tits’ response depends not only on the stimulus but also on the context; cuckoos are absent in winter so hawk-like stimuli at this time are more likely to be hawks. 

The motivation of the signal receiver (value of the resource it is exploiting) may also influence responses to models and potential mimics (Barnett et al. 2007; Cheney & Coˆ te´ 2007). For example, it may pay a more hungry tit to risk a closer inspection of hawk-like stimuli when there is the potential for the stimulus to be a harmless mimic. Previous work on egg discrimination has shown that both great and blue tits, like other species with no history of cuckoo parasitism, will accept eggs unlike their own. This suggests that the egg rejection exhibited by cuckoo hosts has evolved specifically in response to cuckoo parasitism (Davies & Brooke 1989; Moksnes et al. 1991). 

Our results here show that, at least in one context, great and blue tits respond to adult cuckoos as if they were hawks. This raises the possibility that the discrimination by cuckoo hosts of the adult cuckoo as an enemy distinct from hawks, which can be attacked (Moksnes et al. 1991; Duckworth 1991;Welbergen & Davies in press), is also an evolved response to cuckoo parasitism. 

Experiments have revealed that in response to brood parasitism, hosts pay closer attention to the features of their own eggs so they are better able to discriminate against foreign eggs (Rothstein 1982; Lotem et al. 1995). Similarly, hosts may pay closer attention to multiple features of hawks so they can better discriminate cuckoos. Further studies are now needed to test the features used by cuckoo hosts to distinguish cuckoos from hawks and to test whether, despite some host discrimination, parasitic cuckoos still gain from hawk resemblance. Just as host improvements in egg discrimination have been selected for better cuckoo egg mimicry (Brooke & Davies 1988), so perhaps have improvements in their plumage discrimination selected for better cuckoo–hawk mimicry. 

The study followed the guidelines for the treatment of animals in behavioral research and teaching (Association for the Study of Animal Behaviour). The mounted specimens were obtained from licensed taxidermists. We thank Chris Thorne and the Wicken Fen Group, Nancy Harrison, Julia Mackenzie, and Camilla Hinde for color-ringing tits; Jan Davies for making the barred/unbarred underparts for the mounts; John Parker, the director, for permission to work in the Cambridge University Botanic Garden; two anonymous referees for their helpful comments and the Natural Environment Research Council for funding.

N. B. Davies* and J. A. Welbergen

GIANT GROUND SLOTH

GIANT GROUND SLOTH Giant Ground Sloth—The human silhouette in this picture gives an idea of how huge these extinct sloths were. They could even rear up on their hind legs to reach lofty food. (Natural History Museum at Tring) Giant Ground Sloth—The ground sloths were perhaps the most impressive of all the extinct South American mammals. 

Scientific name: Megatherium americanum

Scientific classification:

Phylum: Chordata

Class: Mammalia

Order: Pilosa

Family: Megatheriidae

When did it become extinct? The last giant ground sloths are thought to have died out

around 8,000 to 10,000 years ago.

Where did it live? The giant ground sloths were found throughout South America.

The largest species (Megatherium americanum), the one depicted here, was about the same size as a fully grown elephant. South America is probably the most biodiverse landmass on earth, yet, many thousands of years ago, the fauna of this continent was even more remarkable. A perfect example of this long-gone South American fauna is a ground-dwelling sloth that was the same size as an elephant. This was the giant ground sloth, and it was an immense and unusual animal. 

Fully grown, the giant ground sloth was about 6 m long and estimated of its weight range between 4 and 5 tonnes. Several skeletons (real and copies) of this animal are to be found in museum collections around the world, and one of the most astonishing things about these remains is the size of the bones. The limb bones and their supporting structures are massive and give an impression of a heavy, powerful animal. In life, the digits of the animal were tipped with long claws, which may have been used to grab plant food or even as weapons. 

We know from the skeletons of this animal that the bones of the hind feet were arranged in a very peculiar way, making it impossible for the living animal to place its feet flat on the ground. The animal could certainly rear up onto its hind legs, and perhaps even manage to amble around in this posture, using its thick tail as a strong prop, but it had to shuffle around on the outside of its feet with the long claws pointing inward. The giant ground sloth may have been able to make better progress on all fours, possibly reserving its two-legged stance for feeding or defense. 

As the giant ground sloth is related to the living sloths, it was always assumed that they were gentle plant-eating animals, but some recent, controversial scientific research has shed some light on how this massive beast used its forelimbs. These studies suggest the forelimbs of a giant ground sloth were adapted for fast movement. Such an ability was of little use to a plant-nibbling animal that needed a strong, sustained pull to bring tasty leaf-bearing branches within reach of its mouth. The research suggests that the muscles of the forelimbs were used to power the large claws into other animals, and maybe not only in defense. 

The animal’s teeth also give intriguing insights into the way it fed. They are not the normal grinding blocks that are found in the mouths of plant-feeding mammals. Th ey and the jaws they sit in appear to be adapted for slicing, much like the jaws and teeth of meat-eating animals. The claws and teeth of this giant mammal have led some people to suggest that the giant ground sloth was not a plant feeder at all, but a scavenging animal that used its size to drive predatory animals from their kill before digging into the carcass. 

The image of a 5-tonne brute ambling over to a group of dire wolves, scaring them off, and then devouring their kill is quite fantastic. Regardless of this research, it is decidedly unlikely that this giant lived in this way, and like its living relatives, the giant ground sloth was probably a herbivore, but it may have been able to use its forelimbs and teeth to defend itself. As with almost all of the long-dead animals that once roamed South America, we cannot be certain what brought about the demise of the giant ground sloth. It has been speculated that the arrival of modern humans, with spears and arrows, led to their extinction, but it is reasonable to assume that there was something much more far-reaching happening at the time that wiped these animals out. 

Climate change is one of the usual suspects, and we know that the earth’s habitats were going through some massive changes at the time these animals went extinct. Global temperatures were changing, and land-dwelling animals everywhere were being affected. Hunting may have had an effect, but it may have been minor compared to the ravages of climate change. Today, there are still vast areas of South America where people rarely venture, and some people believe that a species of giant ground sloth may have somehow survived the events that wiped out its relatives and is alive and well in these remote areas. 

Local inhabitants call the beast the mapinguary, and it is said to rear up on its back legs and emit a foul-smelling odor from a gland in its abdomen—not only that but the creature is said to be impervious to bullets and arrows, thanks to some very tough skin on its belly and back. Without a specimen or an excellent photograph, it is difficult to take these stories seriously, but it is worth remembering that previously unknown species of mammal are discovered fairly regularly, and some of them are surprisingly large. If a live giant ground sloth was found today, it would be the zoological story of all time. 

• It is thought that there were around four species of giant ground sloth. The species mentioned here (Megatherium americanum) was by far the biggest. The closest living relatives of these extinct animals are the anteaters, armadillos, and tree sloths. The biggest of these, the giant anteater, would be dwarfed by even the smallest giant ground sloth.

• In 1895, a rancher by the name of Eberhardt found some hide in a cave in Patagonia that turned out to be giant ground sloth skin. The skin was in very good condition, and some people believed that it was from an animal that died relatively recently. When techniques became available to age the skin, it was found to be several thousand years old—it was just that the very dry conditions in the cave had prevented it from rotting. Interestingly, the mummified skin was studded with bony nodules, which probably gave the animal excellent protection from the teeth and claws of predators, and perhaps even the spears and arrows of early humans. 

• It would be fantastic if a species of giant ground sloth had somehow survived into the modern-day, but accounts of the mapinguary may be due to confusion with other animals or derived from folk memories of when humans encountered these animals thousands of years ago.

CATNIP (Nepeta cataria)

Labiatae (Lamiaceae; mint family)

Also known as Catmint, catnep, catrup, catwort, English catnip, field balm, nep, nip

DESCRIPTION

• Catnip, a hardy perennial that grows 0.6 to 1 m (2 to 3 feet) tall, is native from the eastern Mediterranean region to the western Himalayas, central Asia, southern Siberia, and China. Most cats love catnip and purr contentedly, tear delightedly, and roll in ecstasy on its crushed leaves. The generic name Nepeta comes from the Italian town Nepete, where catnip was once cultivated.

• Light green, scalloped, opposite leaves have heart-shaped bases, pointed tips, and velvety, grayish-white undersides. The edible leaves, which have a strong mint-like, warm, pungent, bitterish fragrance and flavor, grow in massed profusion before the plant flowers. After the blossoms appear, the leaves become more sparse.

• Catnip has erect, square, branching stems that are covered in soft hairs. The root becomes quite woody and branched with age. Each spring the root sends up an increasing number of new items, many of which are rather close together.

• Produces spikes of small whitish or pinkish, purple- or red-dotted flowers in midsummer.

• May be grown indoors for winter use.

• Catnip is an excellent honey plant.

CULTIVATION NOTES

• Catnip grows bushiest in well-drained, moderately rich soil, although it also grows well in dry, sandy soil. Add a light layer of compost to the top of the soil before planting. Recommended pH range is 4.9 to 7.5.

Culinary Herbs for Short-Season Gardeners

Thrives in partial shade, but can be grown in full sun.

• Grows easily from seed, which should be started indoors about 6 to 8 weeks before your last spring frost date. Sow seeds no more than 6 mm (¼ inch) deep. Seedlings usually emerge in 8 to 10 days.

• Space transplanted seedlings 30 cm (12 inches) apart.

• Can also be propagated by dividing the roots in the spring or fall, or from softwood or stem tip cuttings. Cuttings from young plants tend to root more quickly, often in just a week. Stem cuttings should be about 10 cm (4 inches) long. Grow rooted cuttings to about 15 cm (6 inches) in a moist medium before you transplant them to the garden.

• Catnip self-sows easily, so be prepared to remove unwanted plants. Weed as Required.

• For bushier plants, pinch flower buds as they appear.

• Usually pest-free, but susceptible to rust and root rot.

• Cats are the biggest problem confronting catnip gardeners. Give young plants a chance to get established by enclosing them in a sturdy chicken wire cage, which will protect them from enthusiastic felines. Cats are drawn to catnip only when the branches are broken or the leaves are bruised, thereby releasing the attractant chemicals, so if the plants aren’t damaged, cats will probably leave them alone.

• Overwinters outdoors up to zone 3.

• Indoor plants should be potted in moist, but not soggy soil that is supplemented with lime. Plants need at least 5 hours of direct sunlight daily. Prune as required, as plants are inclined to become scraggly.

HARVESTING NOTES

• Pick leaves for fresh use at any time throughout the summer, although the taste is milder if you pick the leaves before the plant flowers. Collect the leaves in the morning, after the dew has evaporated.

• To dry catnip, harvest complete stems, including the flowering head and the tender leaves. Cut stems about 5 cm (2 inches) from the ground, and hang upside down in a shady location. When dry, strip off the leaves, crumble them, and store in airtight jars out of the light.

CULINARY USES

• Catnip was a familiar herb in English kitchen gardens as far back as the 13th century. Catnip leaves were once used for rubbing meats before they were cooked, and were chopped and sprinkled into green salads. Snip a few leaves into your salads and see how you like it.

• Add fresh or dried leaves to soups, stews, and hearty sauces.

 

HARVESTING NOTES

• Pick leaves for fresh use at any time throughout the summer, although the taste is milder if you pick the leaves before the plant flowers. Collect the leaves in the morning, after the dew has evaporated.

• To dry catnip, harvest complete stems, including the flowering head and the tender leaves. Cut stems about 5 cm (2 inches) from the ground, and hang upside down in a shady location. When dry, strip off the leaves, crumble them, and store in airtight jars out of the light.

CULINARY USES

• Catnip was a familiar herb in English kitchen gardens as far back as the 13th century. Catnip leaves were once used for rubbing meats before they were cooked, and were chopped and sprinkled into green salads. Snip a few leaves into your salads and see how you like it.

• Add fresh or dried leaves to soups, stews, and hearty sauces. Make a refreshing, soothing cup of tea by pouring 250 mL (1 cup) of boiling water over

15 mL (3 teaspoons) of fresh leaves or 5 mL (1 teaspoon) of dried leaves. Alternatively, add dried catnip leaves, along with dried mint or dried lemon balm, to your favorite black tea.

CRAFT USES

• Sew cat toys and stuff them with uncrushed dry leaves for all your favorite felines.

MEDICINAL USES

• In traditional folk medicine, catnip was used to treat everything from cancer, insanity, nervousness, nightmares, scurvy, and tuberculosis, to colic, diarrhea, flatulence, hiccups, whooping cough, the common cold, measles, asthma, yellow fever, scarlet fever, smallpox, and jaundice. Catnip poultices were applied to hives, and to the sore breasts of nursing mothers.

• Catnip does have sedative qualities and is occasionally used in herbal medicine as a calmative and to treat insomnia.

• Catnip is not used in modern Western medicine.

CAUTIONS

• Catnip has some capacity to cause uterine contractions and stimulate menstruation, so you should avoid it if you are pregnant or suffering from menstrual disorders.

• While a cup of catnip tea is helpful if you don’t sleep well at night, the herb’s diuretic properties mean that your peaceful sleep may be disturbed by an urgent need to go to the bathroom.

• It has been said that catnip may be smoked like marijuana; however, there is no proof that this herb has the intoxicating effects of marijuana. Nevertheless, your suspicions may be justified if young people of your acquaintance seem unusually interested in your catnip plants.

• Bees like catnip, so make sure there are none in the flowers that you pick.

CULTIVARS AND RELATIVES

Here’s a cultivar you won’t have to fight over with your cats quite so much.

• Lemon catnip (N. cataria var. citriodora). Has an appealingly mild lemon aroma, which you may prefer over regular catnip Makes a delicious tea. When candied with egg white and sugar, the leaves make a refreshing after-dinner mint. In the belief that catnip roots made even the kindest person mean, early American hangmen used to eat the roots before executions to harden themselves for their work. While most cats are affected by catnip, not all felines are “nipaholics.” Apparently, a dominant gene is responsible for inheriting the euphoric response. It also appears that cats do not react in their customary delighted way to catnip until they are 3 months old.

Horned Turtle

Scientific name: Meiolania sp.

Scientific classification:

Phylum: Chordata

Class: Sauropsida

Order: Testudines

Family: Meiolaniidae

When did it become extinct? The last of these turtles are thought to have become extinct about 2,000 years ago.

Where did it live? The bones of these extinct turtles have been found on Lord Howe Island, 600 km from mainland Australia and the islands of New Caledonia.

Horned Turtle with their spiked heads and tails, the horned turtles are among the largest and most bizarre turtles ever to have lived. There would be very few people who would fail to recognize a turtle; such is the familiarity of these unusual reptiles. Although the fossil record is full of peculiar beasts, it has been said that the turtles are among the oldest vertebrates to have ever lived.

 Although their skeleton has the same bones like any other vertebrate, they are put together in a very different way. Their body is protected by a bony shell, which is, essentially, a hugely modified rib cage. The strength of this external carapace depends on the species, but it ranges from the leathery dome of the soft-shelled turtles to the almost impregnable shell of the giant tortoises. Also unique is the position of the hip and shoulder girdles, as they are found inside the rib cage. 

These animals are most familiar with being able to withdraw their heads and legs into the safe confines of their shells. The way they withdraw their head allows scientists to identify two groups of turtles: the cryptodires and the pleurodires. The latter is often called side-necked turtles because they bend their long necks into an S shape to keep their heads out of harm’s way. The turtles that people often keep as pets fall in the first group, the cryptodires, and these can pull their heads right into their shells by bending their necks below the spine. 

There’s no doubt that some turtles, especially the land-dwelling species, are very slow, lumbering creatures, characteristics that are often linked to evolutionary failure and poor adaptability. However, nothing could be farther from the truth for the turtles. These shelled reptiles are a successful group of animals that have been around since the Triassic—at least 215 million years (and probably considerably longer)—which makes them much older than the lizards and snakes. Not only are they ancient, but they are among the very few living reptiles that have become almost completely amphibious, only leaving the water to lay eggs (some species of snake also only leave the water to lay eggs). 

Today, there are around 300 turtle species, ranging from tiny, 8-cm tortoises all the way up to the oceangoing giant, the leatherback turtle (Dermochelys coriacea), which can be 3 m long and weigh 900 kg. Even though some truly bizarre turtles are still with us today, they pale in insignificance compared to an immense, land-living turtle that only became extinct in the last couple of thousand years. 

This was the horned turtle, and in life it must have been an astonishing animal. The horned turtle was around 2.5 m long, and it must have weighed in the region of 500 to 700 kg. By comparison, the largest living land-dwelling turtle is the Galápagos tortoise (Geochelonenigra) at about 300 kg and 1.2 m long. Imagine a horned turtle alongside a Galápagos tortoise and you get an idea of the size of this extinct beast. Not only was the horned turtle big, but it also had a very bizarre appearance. Sprouting from its skull were large horns and spikes, the longest of which grew from toward the back of the head and could reach a span of 60 cm. 

This formidable forward armory was combined with the typical tortoise carapace and a heavily protected tail that also sported spines. The horns of this extinct turtle made it impossible for the head to be pulled into the shell during times of danger. It is possible that these horns were used by the turtle to defend itself, but we don’t know what predators lurked on the islands where these extinct reptiles lived. Male giant turtles can be quite aggressive to one another during the breeding season, and maybe the extinct giant used its horns and tail spikes to fight other males for the right to mate. 

As with other island animals, the horned turtles may have grown to great size because there was very little in the way of threats in their isolated home terrain. Alternatively, great size is a simple yet effective defense against many predators. The truth is that we’ll never know the evolutionary force behind the incredible size and appearance of these turtles. What we can be surer of is their diet. Large land-dwelling turtles are slow, heavy animals, so fast-moving animal prey is out of the question. 

We know that the Galápagos tortoise and other terrestrial giant turtles are herbivores that eat a wide range of plant matter. The horned turtle was obviously unsuited to climbing trees or rearing up on its back legs to reach lofty vegetation, so it must have been dependent on the unique, low-growing plants that grow on New Caledonia and the surrounding islands. 

All living turtles lay eggs, and we can assume that the horned turtle was no different, but how it laid them and where will never be known for certain. Perhaps it excavated a pit before laying its eggs and forgetting about them. It is amazing to think that these giant, bizarre turtles roamed some of the isolated islands of the western Pacific into very recent geological times, but exactly why they died out is another mystery. 

We do know that island animals have suffered badly at the hands of humans, and we can be almost certain that the first thing to spring to the mind of the first human who saw these shelled giants was, “Can I eat it?” A slow-moving turtle, regardless of its size, is no match for humans and their various weapons. Lord Howe Island and New Caledonia are small areas of land, and they could never have supported large populations of such big animals; therefore it is very likely that when humans did discover the horned turtle, they wiped them out in a matter of centuries, or possibly even decades. 

• Apart from the way that living turtles bend their necks to hide their heads, we can divide them another way into three groups: there are marine forms, with legs modified into flippers, for example, the leatherback turtle; terrestrial forms, with thick, pillar-like legs, for example, the Galápagos tortoises; and semi-aquatic forms, for example, terrapins and snapping turtles. • 

Many of the living species of turtle may soon follow the horned giant to extinction as they are incredibly endangered. Some of the very rare species only survive in small populations on isolated islands, while the oceangoing species are at risk from fishing hooks, drift nets, and direct hunting. Without complete and active protection, it is very likely that some of the most amazing turtles could be extinct within 30 years. 

• As turtles lead such slow lives, they are among the most long-lived of all the vertebrates. The Galápagos tortoise can live to be at least 150 years old. One famous, long-lived radiated tortoise (Geochelone radiate) was presented to the Tongan royal family in 1777 by none other than Captain Cook. Known as Tu’iMalila, this tortoise died in 1965, at age 188. The longevity of an immense turtle like the horned giant can only be guessed. 

• Further back in the fossil record, in the age of the dinosaurs, there were other extinct turtles that were truly enormous. One of these, Archelon, is only known from 70-million year- old fossils. It was about 4 m long, and the span of its flippers was around 4.5 m. fully grown, Archelon probably weighed in the region of 2 to 3 tonnes. Its large head and powerful bite appear to be suited to eating shelled mollusks such as the extinct ammonites.

Powers of attorney

Around the late-60s, many perfectly fit men and women wondered whether it might be sensible to give power of attorney to someone they trust. This involves authorizing another person to take business and other financial decisions on their behalf, on the basis that any such decisions would reflect the action that they themselves would have taken. Until a few years ago, the power could only be used where the individual was unwilling rather than incapable of acting for him/herself. So in effect, just at the time when the power was most needed, it ceased to exist. Thanks to a law known as the Enduring Powers of Attorney Act 1985, and the more recent Lasting Powers of Attorney an enduring power is not automatically revoked by any subsequent mental incapacity, but can now continue, regardless of any decline, throughout the individual’s life. 

(NB: An ordinary power of attorney would be revoked by subsequent mental incapacity.) To protect the donor and the nominated attorney, the Act clearly lays down certain principles that must be observed, with both sides signing a declaration that they understand the various rights and duties involved. The Act furthermore calls for the power to be formally registered with the Public Trust Office in the event of the donor being, or becoming, mentally incapable. As stated above, the Enduring Powers of Attorney have been replaced by Lasting Powers of Attorney (LPA), to coincide with the implementation of the Mental Capacity Act 2005. 

In effect, LPAs enable individuals to give their attorney power to make decisions about their personal welfare, including health care, when they lack the capacity to make such decisions themselves. Enduring Powers of Attorney, set up before October 2007, are still effective. However, if you have not yet set one up but are planning to do so, you will now need to apply for the new LPA instead. As any lawyer would explain, the right time to give power of attorney is when the individual is in full command of his/her faculties, so that potential situations that would require decisions can be properly discussed and the donor’s wishes made clear. For the Lasting Power of Attorney to be valid, the donor must in any event be capable of understanding what he/she is agreeing to at the time of making the power.

brown-backed shrike

Contemporaneous eggs of different color types of brown-backed shrike can be smooth in the interference experiment The fertile eggs are hatched, but the out-of-phase eggs are rejected, and the basis for the judgment of the parent birds may be Egg color. There are two possible reasons for this phenomenon: one is two-color types Brown-backed shrike can distinguish out-of-phase eggs, but due to differences in the timing of ovulation Largely causes hatching and energy investment contradictions in the allocation of feeding time The second is that the two-color brown-backed shrike uses the out-of-phase eggs as parasites Egg rejection. 

Moskat & Fuisz (1999) put fake cuckoo eggs (blue Eggs with better color and imitation) are placed in red eggs during laying and early hatching. Among the back shrike nests, the coping strategies shown by the red-backed shrike include driving Eggs from abroad (71.2%), abandonment of original nests (19.2%), acceptance of foreign eggs Come eggs (9.6%), and the rejection rate of blue eggs is higher than that of eggs with better imitation; In the laying period, the eggs with better imitation are mainly abandoned, and in the incubation period.

The foreign eggs are expelled. The results of this experiment showed a phenomenon of abandoning the nest, and the performance of heterochromatic and homochromatic types is more consistent. brown-backed shrike pair nest Insensitivity to the number of mid-eggs, increased contemporaneous homochromatic eggs, or intentional or unintentional Reducing the number of eggs will not affect their nesting. But at the same time, the brown-backed shrike nest will be abandoned in the case of strong human disturbance. 

According to local villagers, the Brown-backed shrike is seen navigating the transfer of chicks in old nests during brooding to the new nest. Judging from the current situation, the white spots or white edges on both sides of the wings of birds are not It is easy to be found by natural enemies or predators, and it is easier to appear white above and below It was discovered by natural enemies, so white spots and white borders on the side of the body may play a role in the individual The effect of recognition, especially the recognition of the parent by the offspring during the feeding period. 

Book The experimental foster child chicks were nurtured normally in the foster parent's nest, and after development Follow the activities of the righteous parent and learn their behavior, its later spread and the relationship with the righteous parent The relationship needs to be further studied in the future. The sexual selection hypothesis suggests that plumage polymorphism may be due to female Preference for salient morphologies and predation pressure favoring concealed morphologies produced and maintained. In this case, the plume polymorphism reflects the relative dominance of the individual, which is correlated with the expression of bodily signals Consistent, that is, the degree of pigmentation represents different status, such as health and nutritional status. 

However, prominent patterns favorable to sexual selection may be due to high predation risk or used to produce and maintain significantly high color energy expenditure and balance with non-salient forms (Endle, 1980). A total of 21 brown type, 9 black type, and heterozygous type were found in the plot. 10, including 10 heterozygous nests, 6 black-type females, many The species-colored brown-backed shrike breeds synchronously, and there is no preference for the same species of shrike The opposite sex is paired. In summary, we included in 2006-2008 The 44 nesting birds found in the plot were brown and black broodstock. 

In the breeding nest, the ratio of black-type females to brown-type females was 20:24. From the perspective of the sexual selection ratio, the ratio is similar, and there is no large ratio. That is, females show no preference for males of different color types. from reproduction From a physical point of view, we have not been able to determine the brown-backed shrike feather machine control, maybe plumage polymorphism is not related to selection, it may be simply a neutral relationship to a physiological or ecological characteristic or non-adaptive traits (Galeotti, 2003) Both color types are absent in both reproduction and brooding during the reproductive process Isolation occurs. 

The generally accepted concept of species holds that a species is Nature is able to mate, produce fertile offspring, and exist with its population reproductively isolated groups. Integrated reproductive isolation and morphological traits, behavior Evidence of differentiation, we support that black shrike is just one of the brown-backed shrikes Chromotype, rather than an independent species point of view. About Black Type Source and Feather Color Genetic laws and other issues still need to be investigated in the future for more different types of brown. 

The accumulation of research on Shrike individuals, from morphological, ecological, genetic Comprehensive research in multiple disciplines such as science and geography. Acknowledgments: Jiang Yanqiong assisted in the completion of the control experiment of easy eggs and easy chicks work, the Guangdong Haifeng Bird Nature Reserve provided the Thank you for your help!

Bird that sounds like a turkey?

Please write an article about what bird sounds like a turkey. A lot of people think that turkeys sound like they’re gobbling or clucking but there are actually many different types of birds that sound like turkeys. Some birds have a deep voice while others have a high pitched one. There are also some birds that sound more like ducks than turkeys. You can learn more about these birds by writing an article on them.

The blackbird is a songbird, which means it sings and makes music. It is found in most parts of the world except Antarctica. Its name comes from its black coloration. They live in trees and bushes. Their songs are often described as “liquid notes” because of their musical quality.

The great tit is a common European passerine bird. It is a member of the family Paridae. It is known for being very social, and will often form flocks. This bird is named after the great tit (Parus major). Great tits are native to Europe, Asia, North Africa, and North America.

The blue jay is a large American crow-like corvid. It is a common species throughout much of Canada and the United States. Blue jays are omnivorous, eating both plant material and animal matter. They are highly intelligent, and have complex communication systems.

The cuckoo is a brood parasite. Cuckoos lay eggs in other birds' nests, where they hatch out and raise the young as if they were their own. In return, the host parents feed and protect the cuckoo's offspring until they fledge. The term "cuckoo" comes from the Old English cucu, meaning "rooster."

The domestic chicken is a domesticated fowl, descended from the red junglefowl (Gallus gallus), which is itself a domesticated subspecies of the grey junglefowl (G. g. murghi) of Southeast Asia. Domestic chickens are raised primarily for meat, although egg production is another important factor. Chickens are commonly kept as pets, especially in urban areas.

The domestic duck is a domesticated version of the mallard. Ducks are popular as waterfowl due to their ability to swim well and dive. They are usually kept as pets, but may be hunted as gamebirds.

The domestic goose is a domesticated version, or variant, of the Anatolian landrail. Geese are usually kept as pets; however, they may be hunted as game.

The domestic pigeon is a domesticated version or variant of the rock dove. Pigeons are usually kept as pets. However, they may be hunted for sport.

The domestic quail is a domesticated version (variant) of the bobwhite quail. Quails are usually kept as pets and eaten as food.

The domestic rabbit is a domesticated version/variant of the hares. Rabbits are usually kept as pets or used for hunting.

The domestic turkey is a domesticated version and variant of the Meleagris gallopavo. Turkeys are usually kept as pets but may be hunted as food.

The European starling is a domesticated version. Starlings are usually kept as pets though may be hunted as game birds.

The guinea pig is a domesticated version that originated in South America. Guinea pigs are usually kept as pets although they may be hunted as food animals.

The kookaburra is a domesticated version originating in Australia. Kookaburras are usually kept as pets whereas they may be hunted as prey.

The ostrich is a domesticated version originally from southern Africa. Ostrichs are usually kept as pets with some individuals being hunted as food.

The domestic dog is a domesticated version derived from wolves. Dogs are usually kept as pets as well as used for hunting.

 

Questions

Questions used across top search results:

• How can you tell a male from a female wild turkey?

A male has a redhead and neck, while a female has a grayish-brown head and neck. Males also have a black tail tip, while females do not.

What does a turkey call sound like?

A turkey gobbles when it wants to attract mates. A turkey will make this noise by opening its mouth wide and making a loud “gub” sound. This sound is made by forcing air through the nasal cavity.

How long does it take for a turkey to reach sexual maturity?

It takes about two years for a turkey to mature sexually.

How old is a wild turkey?

Wild turkeys live up to 20 years old.

Where did the name turkey come from?

Turkeys were first called turkies because they were thought to be related to the Turdus genus of thrushes. In 1580, the English word turke was used to refer to 

Dark-throated Oriole (Oriolus xanthomas)

 Size: About that of the Myna.

Field Characters:

Dark-throated Oriole is a species of family Oriolidae. The brilliant golden-yellow bird has a jet-black head, throat, and upper breast. It has black in wings and tail, as sexes alike. It is found singly or in pairs, arboreal, in wooded country.

Distribution:

The whole of the Indian empire expected the arid portions west of a line from Kathiawar through Mount Aboo to the Sutlej Kiver. In the Himalayas, the bird can be found up to about 4,000 ft. Three races are recognized for differences in size and details of coloration, viz., the largest northern xanthornus, the intermediate peninsular maderaspatanus, and the smallest Ceylonese ceylonensis. It is resident over the greater part of its range but also moves about locally to some extent.

Habits:

This oriole, like the last, is a bird of well-wooded country and groves of large trees, often in the neighborhood of human habitations. It has a variety of loud melodious calls which in general are very like those of the Indian Oriole. A harsh monosyllabic note commonly uttered is mistaken for one of the Tree-Pie's. Otherwise, there is no appreciable difference between the habits of the two species. The natural habitat of this oriole is subtropical or tropical moist lowland forests.

Nesting:

The principal months in India are from April to July, but in Ceylon, it apparently breeds from October to May. The structure and size of the nest do not differ from those of the Indian Oriole, but the eggs are somewhat smaller, pinker, and less glossy. Orioles of both species, along with such other mild-mannered birds as doves and babblers, often build in the same tree as holds a nest of the Black Drongo.

That this is by design rather than accident can scarcely be doubted considering how frequent the occurrence is. It is certain also that the birds must thereby enjoy a degree of protection against marauders like crows and tree-pies. King Crow will tolerate the proximity of his harmless dependents with complacence, but a crow has only to show himself in the precincts of the nest tree to be furiously set upon and beaten off by the valiant kotwal and his wife.

Other Names

The other names of Dark-throated oriole are black-throated oriole, black-headed oriole, and Malaysian oriole. Also, the black-headed oriole shouldn’t be confused with the species of a similar name, (Oriolus larvatus).

BENNU BIRD

The Bennu bird, albeit little known nowadays, is an extremely important figure in the solar myths. The first mentions of Bennu date from the Pyramid Texts of the Old Kingdom: the bird was associated with (or was one of the forms of) the creator god Atum, which in turn was an aspect of the sun god Re (Atum was the evening sun, Khepri the morning sun and the nominal Re the midday sun). Later, during the Middle Kingdom, Bennu was considered the ba of the sun god Re, which originated Atum. The ba is one of the souls that make up things in Egyptian beliefs; it is roughly equivalent to our notion of personality. Bennu is said to have flown over Nun, the primordial ocean, right before creation. He finally perched on a rock and let out a loud cry (in the sense of the usual animal call), which broke the primeval silence. This first cry was said to have determined what was and what was not to be in the soon-to-be-unfolded creation by the hands of Atum. 

Very little is known of Bennu’s cult, but his role in the solar mythology of Heliopolis probably made him very important in the region’s cults. Bennu’s titles were “He who Came into Being by Himself” and “Lord of Jubilees”, reflecting, respectively, his selfgenerative birth and its long life. Bennu is usually depicted as a heron (Fig. 5A), sometimes atop of the benben stone (the rock or mound where it first perched, which represents Atum/Re) or on a willow tree (which represents the god Osiris). But where did Osiris come from in this story? Bennu became linked with Osiris as a symbol of anticipated rebirth in the Underworld; as such, the bird is sometimes depicted wearing Osiris’s atef crown (a feathered white crown; Fig. 5A). Rarely, Bennu is depicted as a heron-headed man. Bennu appears as a persona only in the very first game in the series (P1). 

Its depiction in the game is completely stylized and rather bizarre (Fig. 5C), not being very reminiscent of a heron at all. However, the official artwork of the Bennu in the Shin Megami Tensei series is more similar to the Egyptian drawings (compare Figs. 5A and 5B). Nevertheless, it has a short neck and a long and curved beak, looking more like a hybrid of a vulture and an ibis than a proper heron. In addition, it wears not the atef crown of Osiris, but the headdress of the goddess Hathor (the sun disk amid cow horns), which has nothing to do with the Bennu. Archaeological remains found in the United Arab Emirates, dating from the Umm an-Nar period (2600–2000 BCE), contained bird bones, some of which belonged to a large heron. 

These bones were deemed to belong to a new species, which was named Ardea bennuides Hoch, 1979 (its common name is “Bennu heron”). This now extinct species is considered to have been the inspiration for the Bennu – for an idea of what the animal might have looked like, take a look at the grey heron (Fig. 5D), which belongs to the same genus. The date of the remains of the Bennu heron coincides with Egypt’s Old Kingdom and First Intermediate Period (Table 2). However, the Bennu only started to be depicted as a heron later in Egyptian history, during the New Kingdom. Back in the Old Kingdom days, we find another bird that might have been the first inspiration for the Bennu – and it has absolutely nothing to do with a heron. 

This bird is the yellow wagtail, Motacilla flava Linnaeus, 1758 (Fig. 5E), which in the Pyramid Texts is considered a representation of Atum himself. A Finally, I should say something about another famous mythological bird, the phoenix. The Greek historian Herodotus visited Egypt during the 5th century BCE. There, he learned about the Bennu bird from the priests and called very modest bird for such an important role, perhaps? it Phoenix in his native language (the name was likely derived directly from “Bennu”). In later Greek tradition, the phoenix was often likened to an eagle, but kept the characteristics of its origin: its role as a sun-bird and a symbol of resurrection, its self-generative birth and its long life. These characteristics might have given rise to the legend that the phoenix is reborn anew in a fiery conflagration, like the sun rising at dawn. As such, we may consider that Bennu is also present in the games P2-IS and P2-EP, under the guise of “Phoenix”. In this depiction, the persona is clearly following the Greek eagle tradition.

WHAT'S THE DIFFERENCE BETWEEN A SPRING AND AN ARTESIAN

 People who live in the city do not have to worry about wells or springs. The city supplies them with water. But out in the country and in some suburbs. Obtaining a water supply may be quite a problem. Such water may come from a spring or a well. A spring is a water that flows from a natural opening in the ground during the rainfall, part of the WELL? Water soaks into the soil and rocks through small spaces and cracks and is pulled down by gravity as far as the openings in the rocks will allow At different levels below the surface of the land there is a zone where all the openings in the rocks are completely filled with water.

This is called "the underground zone". The upper surface of it is called the water table". In valleys or other low places in the land surface, below the water tables. Springs occur where there are cracks in the rocks. In other words, the water that has been stored up there escapes as spring water. Some springs flow all year because they receive water from deep within the ground-water zone. Other springs flow only in the rainy season when the water table is at its highest level. 

An artesian well is a well from which the water bubbles up naturally above the surface of the earth. An artesian well is formed when a layer of loose rock gravel or sand is sand between two layers of solid rock. The loose gravel or sand has spaces to hold the water. So we have three lavers-solid rocks above and below and a porous layer that is like a pipe between them. These three layers are not horizontal, they lie at an angle. Water enters the middle layer at the top end. Farther down, if an opening is made, there is a pressure that makes the water spurt out and we have an artesian well.

The British Magpies

One for sorrow, two for joy but what do you get for 100 or even 150 Magpies Pica pica? Groups of this size are not uncommon, and indeed the antics of large gatherings of Magpies were described by the Reverend Darwin Fox to his cousin, Charles Darwin, who subsequently wrote:

“The common magpie used to assemble from all parts of Delamere Forest, in order to celebrate the 'great magpie marriage'. They had the habit of assembling very early in the spring at particular spots, where they could be seen in flocks, chattering, sometimes fighting, bustling, and flying about the trees. The whole affair was evidently considered by the birds as one of the highest importance. Shortly after the meeting they all separated, and were then observed to be paired for the season.” (Darwin 1871)

The Magpie is a small-to-medium-sized member of the crow family (Corvidae).  The adult males weighed 248 g and adult females 223.3 g. The sexes are identical in plumage, but the size difference between the sexes is often apparent if they are seen side by side. The Magpie has a wide geographic distribution, breeding throughout most of Europe and Asia, North Africa, and western North America.

Geographic variation exists, generally in terms of body size and the relative amounts of black and white plumage. Inevitably, a species with such a broad geographic range occupies a wide range of habitats, from the semi-arid desert in North Africa, and the prairies of North America, to Alaska's boreal forests. In Britain, its habitat includes the lush farmland of lowland England and the windswept moors of the Peak District. The estimated breeding population of Magpies in Britain and Ireland to be about 250,000 to 500,000 pairs.

This is a resident population, and there is no immigration into Britain from the Continent. In Britain, the Magpie has undergone a population increase during the past 40-50 years. Therefore an increase has also resulted in the spread of Magpies into the urban areas.

This increase in abundance has been met with a variety of responses: obviously, Magpie enthusiasts have welcomed it, but they are pretty thin on the ground. The commonest response has been concern over song-bird populations (see page 598). Ringing recoveries show that Magpies rarely undertake long-distance movements. That the median distance between the natal nest and first-breeding location was just 447 m, equivalent to moving 1.8 territories.

As with other passerine species, females tended to move farther (497 m,) than males (350 m), although this difference was not statistically significant. The median distance between annual breeding attempts was even less: males 15 m and females 27 m. A significantly higher proportion of females bred in more than one territory during their life (13/48; 27%) than did males (5/ 64; 8%). This occurred because males which lost their partner were still able to defend their territory alone and invariably remained there.

In contrast, a lone female could not maintain a territory, so, if she lost her partner, she usually moved to another territory to repair. These results probably reflect Magpie dispersal fairly accurately; we regularly searched all surrounding areas for color-ringed birds, and, in ten years of enthusiastic Magpie recording by the Sheffield Bird Study Group, we had only four reported sightings of individuals more than 2 km from where they had been ringed. Magpies are monogamous, and a breeding pair defends an all-purpose territory.

In most studies of Magpies in Britain and the Continent, territories average about 5 ha in extent. The population can be divided into two sectors, the breeders and the non-breeders. In some areas, non-breeding individuals may comprise 20-40% of the total Magpie population.

Non-breeders are usually one-year-old and two-year-old birds (rarely three- and four-year-olds) that live as part of a loose flock ranging over the territories of established pairs. The flock is organized into a dominance hierarchy, with males generally being dominant over females.

This occurs partly as a result of the difference in body size between the sexes. The situation is rather more complex than this: the date that a young Magpie entered the non-breeding flock also had a marked effect on its status, with late arrivals achieving the lowest status. The pattern is by performing an ambitious experiment that involved hand-rearing and releasing 44 Magpies into the study area at different times. This result also explains why late-hatched young had the lowest likelihood of surviving to breed.

Providing that they survive long enough, Magpies start to breed in their first or second spring: mean ages of first breeding were for males 1.6 years and for females 1.4 years (this difference is not significant). Breeding Magpies in our study area (based on re-sightings of color-ringed birds) had a life expectancy of 2.0 (female) to 3.5 years (male).

The oldest Magpie we recorded died in its 9th year. However, the ringing recoveries provide a similar longevity record: 9.7 years. These data were obtained in an area where Magpies were unmolested; obviously, mortality rates will vary in different areas.

Diet and feeding behavior

Magpies are omnivores and will eat pretty well anything: we have seen them eat pears, dog faces with relish, attack a mole Talpa europaea, catch, kill and eat voles (Microtinae) as well as eating the berries of whitebeam, acorns, and household scraps.

It is difficult to build up an accurate picture of any species' diet because different study techniques have different biases associated with them. The stomach contents of shot Magpies and analyzed Magpie pellets and droppings. During summer, the bulk of the adult and nestling diet comprised grassland invertebrates (beetles, caterpillars, spiders, leather jackets, and earthworms). In winter, much more vegetable matter (e.g. seeds, bulbs) was eaten. A very little evidence that Magpies took many songbird eggs.

Like many other crows, Magpies hoard excess food. There is, however, not the slightest evidence that Magpies are specifically attracted to (or steal) bright objects such as money or rings. The food-hoarding behavior of the Magpies has some detail. Most food-hoarding by Magpies is short-term, with items recovered within just one or two days, unlike the Jay ‘Garrulus glandarius’ and nutcrackers Nucijraga, which cache acorns and pine seeds, respectively, in the autumn and eat them in the following breeding season. All but one of 3,184 caches by Magpies were made in the ground, usually in areas of short grass.

A Magpie typically filled its pouch with food, flew or walked to the cache site, and then made a hole in the ground with its bill. It then ejected the food into the hole and covered it with a stone, twig or piece of dead grass. We found caches extraordinarily difficult to relocate. On several occasions, we watched a Magpie hoarding food and maintained a fix on the hoarding place through a telescope while the other person walked into the field of view. This narrowed our searching area to about 0.2 m2, but we rarely found caches without a lot of trouble.

So how do Magpies relocate their caches? Although some experiments that Marmioc their sense of smell to find hidden food, they probably rely mainly on their well-developed spatial memory to relocate caches. We regularly saw Magpies fly directly to a point in their territory and recover cached food; unlike us, they found the food immediately, without having to dig up half the field. This strongly suggests that they could remember its precise location.

Squirrels and the Acorn Woodpecker store food in a single 'larder' which they then defend against other animals, but Magpies are 'scatter hoarders', dispersing their caches over a fairly wide area. Territorial Magpies hoarded within the territory and (by definition) non-breeders cached food within their home range, but these two categories of birds had different hoarding strategies.

Territorial Magpies made their caches much closer together than did non-breeding Magpie. To determine whether this spacing was adaptive, some field experiments; to test the idea that the difference in cache spacing was important in terms of the birds' likelihood of recovering them.

Grids of artificial caches at different densities were (laboriously) set out. Each cache, which consisted of 7.5 g of grain, had a two-pence piece placed under it, so that it could be relocated using a metal detector, but without providing any visual cues for Magpies. After four days, the grids were re-examined to record the proportion of caches still present. The experiment showed that the caches placed closest together suffered the greatest losses.

Subsequent observations showed that Magpies spaced their caches according to the rate at which the artificial caches had been lost in those same territories. In other words, the Magpies were able to assess the intensity of cache loss (probably through the number of other Magpies in the immediate vicinity) and space their caches accordingly. A territorial Magpie could afford to space its caches close together because no Magpies (other than its mate) were likely to enter the territory and raid the caches.

On the other hand, non-breeders generally foraged in a flock, and, once one Magpie discovered a food item (from a cache or otherwise), other flock members rapidly congregated in that area. In other words, if a non-breeder made its caches as close together as a territorial Magpie, it would almost certainly lose much of its hidden food to other flock members. By caching at a low density, flock Magpies reduced this risk.

Breeding biology

Nest-building may start very early; we have occasionally seen Magpies building on mild days in late December and early January, even though eggs are not laid until late March. Magpies may build a new nest or they may re-use or add to an old one. If a new nest is built, it is constructed in four distinct stages: an anchor, a superstructure, a mud bowl, and a lining. Once the Magpies have decided upon a nest site, the first place twigs there; these are followed by mud or clay, which forms the anchor.

Twigs are added to this to make the superstructure, including the domed roof. Once the superstructure nears completion, the mud bowl is started; and when this is finished the lining of hair and rootlets is added. Nest-building may be spread over two months, or a new nest may be knocked up in less than a week, Well-constructed nests are very durable and may last many years. One can tell quite a lot about the owners just by examining the nest.

One-year-old Magpies and first-time breeders generally build very poor nests—often not much better than bulky nests of Woodpigeon Columba palutnbus. In contrast, established breeders sometimes build fortress-like nests. One of our long-lived color-ringed birds built a particularly robust nest every year; the roof was especially dense, such that the nest contents were completely concealed from the outside.

Moreover, the roof was interlaced with spiky twigs of hawthorn Crataegus, making nest inspection particularly difficult for us. Most Magpie nests are roofed and found that 61 out of 79 nests (77%) were roofed and that 66% of those produced at least one chick, whereas only 5% of nests without a roof produced young.

Nests are built in a variety of locations, from the tops of 30-m beeches to scrubby willows Salix or hawthorns just a meter or so high. In some parts of the study area, Magpies had a wide choice of trees in which to nest; in others, at higher altitudes, there was little or no choice, since many territories contained only a single tree or bush. In treeless urban areas of Sheffield, we have found Magpie nests in British Rail watchtowers, on electricity pylons, and inside factories.

Egg-laying commenced in late March, and the annual median laying date (the date on which 50% of pairs had laid their first egg) varied from 10th to 24th April. Much of this variation was attributable to spring temperatures: in warmer springs, laying started earlier, and this, in turn, was almost certainly the result of warmer temperatures increasing the availability of the Magpie's invertebrate food.

Magpies are single-brooded, and the clutch consists of three to nine eggs; the mean number varied only slightly between years, from 5.5 to 6.3 eggs. Clutch size also varied within a season, with the earliest breeders generally producing the largest clutches. This in turn was a result of older Magpies breeding earlier and producing larger clutches than young Magpies.

If the first clutch is lost, a replacement will be laid, and, in our study area, almost always in a new nest. Replacement nests were always within the territory, but were often difficult to find, because, unlike first nests, they were usually built when the trees were in leaf. Magpies would lay up to four clutches in a season if necessary.

Incubation lasts for about 18 days and is undertaken entirely by the female. The male feeds the female on the nest, and the extent to which he does this helps to determine their likelihood of success. Females that are not looked after by their partners have to leave their eggs more often to feed themselves, and this increases the risks of the eggs being taken by predators.

There were two main causes of egg loss: small boys (which we cured of the habit rapidly) and Carrion Crows. Carrion Crows and Magpies are arch enemies; they compete for food and probably nest sites, and Carrion Crows will eat Magpie eggs or chicks at any opportunity. As a result, Magpies breeding close to a pair of Carrion Crows generally had relatively low breeding success. In one year, we estimated that over 30% of all Magpie breeding attempts failed as a result of Carrion Crow predation.

The Carrion Crow catches an adult Magpie in flight and kills it. Magpie nestlings leave the nest after about 24 days. We weighed, measured and color-ringed nestlings at 14 days after hatching; later than this and we would have risked them 'exploding' from the nest. After fledging, the young remain with their parents for about six weeks; in one or two cases (out of about 1,000) young Magpies stayed with their parents in the territory until the following breeding season. In our study, breeding success averaged about two nestlings per pair, although some pairs were very successful and raised large broods, whereas others failed to rear any young at all.

This is reflected in the lifetime reproductive success of Magpies: 60% of females and 40% of males failed to produce any young during their lives. During the course of our study, the Magpie population doubled, examined the effect of this increase in Magpie density on breeding success. Interestingly, there was no effect on either clutch size or breeding success, but there was a strong effect on juvenile survival.

The proportion of Magpies surviving through their first year was negatively (and significantly) correlated with breeding density. This indicates that density-dependent mortality of juvenile Magpies is one of the factors regulating Magpie populations.

Reproductive behavior

Many bird species, like the Magpie, traditionally regarded as monogamous, are now known to be less monogamous than once thought. The female’s trouble they went to protect their paternity. If similar things went on among birds: it soon became apparent that they did. Established pairs of Magpies live in their territories all year round, but the male and female may operate independently for much of the time.

From just before and during egg-laying, however, the male never lets the female out of his sight, remaining close beside her and following her every move. If she flies, he follows. If she walks behind a wall, he moves so he can still see her. Why should the male be so keen to keep close to his partner at this time?

The answer is that he is guarding her against the sexual advances of other males. Male Magpies are remarkably randy and regularly try to mate with neighboring females. On several occasions, we saw a male sneak (literally) into the adjacent territory, using the vegetation as cover, approach the female, and attempt to mate with her.

Most of these extra-pair copulation attempts were unsuccessful because they were cut short by the male partner chasing the intruding male. The closest that I saw a male come to being successful occurred when a guarding male fell asleep. His head lolled onto his breast, and, in so doing, fell below the top of the wall so that he could no longer see his female, who was foraging close by. Within a second or two of this happening, the male from the adjacent territory flew across and mounted the female. I think that local contact was not achieved; the female called during the mating attempt and this alerted her partner, who woke up and flew down and chased the other male and his partner.

This would be the end of the incident, but there was a further development. When this extra-pair copulation attempt occurred, the female had already laid part of her clutch, but her partner immediately started to build a new nest in a tree adjacent to the original nest. The female laid the rest of her clutch in the original nest but never started to incubate. Instead, she subsequently produced a repeat clutch in the new nest. The interpretation was that the male partner did not want to risk the fact that his female may have been fertilized by the other male. Hence, waste his effort by rearing chicks that may not have been his own.

Subsequent studies have shown that both mate-guarding and extra-pair copulations are widespread among many bird species and that such extra-pair mating can result in extra-pair paternity. Magpies showed some interesting extra-pair responses to a tame, caged female placed in their territory.

If the male approached the tame female alone he invariably courted and attempted to mount her. But if the pair approached the 'intruder' together, they were always aggressive towards her. Often the male would approach on his own and start to court the female, only to be followed a minute or two later by his partner.

As soon as he heard his female approaching, the male's courtship switched to aggression. The human analogy is obvious. It is perhaps surprising that we have actually seen as many, or probably more. The extra-pair mating attempts then have pair mating. The courtship between Magpies is infrequent. It consists of the male circling the female with his wings flapping and tail held high and twisted to one side. Mating is brief (1-2 seconds) and very rarely seen. On the basis of prolonged and detailed field observations, Magpies probably copulate only about three times for a clutch.

Groups and Territories

Magpies are regularly seen in groups, from half a dozen to over 100 birds, and these groups may occur for a variety of reasons: mobbing, feeding, roosting, and 'ceremonial purposes. Magpies may assemble to mob predators such as foxes, cats, weasels, rats, or owls, but mobbing groups are usually small (up to ten birds) and disintegrate fairly quickly.

Non-breeding Magpies live as members of a flock, but these flocks are very loose, and all members come together only if food is locally abundant (e.g. if muck has recently been spread in a field). In our study area, the Magpie population density was high; the largest feeding flocks that we saw consisted of about 50 birds, but feeding groups of 20-30 were not unusual. Groups also occur where territories abut, and the pairs perform parallel walks along their respective boundaries.

If the territory boundaries were unknown to the human observer, these birds would appear to be a 'group'. The largest groups occur at roosts or pre-roost gatherings, where over 100 may congregate. In our study, most Magpies roosted in small groups (of about 30 individuals) close to or within their daytime range, but, just 2 km away, a roost of 150-200 Magpies existed throughout the autumn and winter. These birds roosted in hawthorn bushes in an area of dense scrub, but they entered the bushes only just before dark. Prior to this, the birds assembled in a pre-roost gathering in a field some 200 m away.

The observations support the idea that Magpie communal roosts contain mainly non-breeding Magpies while established breeders roost singly or in pairs within their territory. The final category of the group is that about which Darwin wrote, now generally known as 'ceremonial gatherings'. These groups are rarely as large as pre-roost gatherings, although they have sometimes been depicted as such.

The average size of 225 ceremonial gatherings is to be nine Magpies (range 3-24). Gatherings occurred at all times of year but were most frequent during January to March (i.e. just before the breeding season). They also tended to occur more frequently in the morning than in the afternoon. The function of ceremonial gatherings has been discussed for a long time and suggested functions included pair formation and competition for nest sites or territories. Only through having individually color-marked birds of known status were we able to work out what was going on in these gatherings.

Initially, most gatherings that we observed were in progress when we first saw them, but we soon discovered that the key to understanding them was to see them from their inception. Gatherings were usually initiated by one or two non-breeding Magpies, usually the most dominant members of the non-breeding flock. Single initiators were always males, and 80% of groups of two were paired birds. Gatherings were started in the following way: the bird would fly unusually high and would then swoop directly down into occupied territory.

There they would instantly be met by the territory owners, who would call and chase them. This in turn would attract non-breeders in the vicinity and the holders of adjacent territories (only rarely did breeders 'leapfrog' territories to join a gathering). Almost all the 'action' during a gathering occurred between the initiators and the territory owners. The other birds were present as mere spectators. Sometimes, however, one of these would be accidentally drawn into the chasing and calling if it was attacked by mistake, resulting in the apparent 596

The Magpie chaos typical of these gatherings means the duration of gatherings was ten minutes and the maximum was 70 minutes. In most cases, the gathering soon subsided and the initiators left the territory, followed by the other individuals dispersing. What is happening is as follows. Competition for territories is intense. In our study area, all available space was occupied by territorial Magpies and a large pool of potential breeders (the non-breeding flock) existed. Instead of passively waiting for a vacancy to arise, say through a territory owner dying, the most dominant flock birds attempted to obtain a territory by force.

They visited territories in a deliberately provocative manner, confronting the owners in order to monitor the strength of their aggression. In most cases, the initiators quickly backed down and left, but, occasionally, they found a pair whose territory was less strongly defended. They then appeared to press home an attack, harassing the owners with repeated visits and prolonged chasing. In a few cases, the territory owners were evicted, in others, the gathering initiators carved out a very small piece of ground for themselves. If this occurred, it was usually at the junction of two or three territories (the point where the defense was weakest).

Once they had obtained a foothold there, the invaders gradually expanded the territory until, after a week or so, it was sufficiently large for breeding. We estimated that a third of the territories were obtained in this way. Evicted territory holders usually disappeared (which probably means they died) or became members of the non-breeding flock (which was genetically equivalent to being dead, for none of these birds ever bred again). Why did other Magpies turn up as spectators at gatherings? I think the reason is that it was in the interests of all nearby birds to know what was going on. A change in territory ownership could, through a domino effect, lead to a change in fortunes for these other birds as well.

A change in the ownership of one territory sometimes resulted in a succession of subsequent changes. There were two other ways in which Magpies could obtain territories:

(i)                 Replacement

(ii)               What we called 'squeezing in.

The replacement was straightforward: one or both members of a territorial pair died or disappeared and their places were taken by non-breeders, without a gathering.

Squeezing-in consisted of pairs taking advantage of the decline in territorial aggression that occurred after egg-laying. These birds simply squeezed in at the junctions of existing territories, without a gathering. Those that squeezed in, however, usually did so too late to breed in that season.

Bird and territory quality

The effect of bird and territory quality on reproductive success was examined in detail. This showed that some territories were occupied more (and others less) than expected by chance, a result that suggests that territories differed in their quality.

Furthermore, analysis of territory composition showed that the number of years in which the territory was occupied was positively (and significantly) correlated with the relative amount of grazing land (short grass with cattle or horses) in the territory. Several other lines of evidence indicate that this is a good measure of territory quality:

(i)                 Magpies obtain most of their food from such areas above.  

(ii)               The breeding success was positively correlated with the relative amount of grazing land in the territory. It is also found territory quality to be important in affecting the Magpie's breeding biology: his studies indicated that food availability determined the quality of a territory.

The importance of the experiment is by providing some Magpies with the additional food prior to egg-laying. Fed birds lay earlier, produced larger eggs and clutches, and reared more young than did unfed birds. In our study area, territory quality was obviously important, found that bird quality played a bigger part than territory quality in determining breeding success.

The disentangle the effects of territory and bird quality on breeding parameters (such as clutch size and laying date). That is by looking at these parameters when the same territories were occupied by different birds. However, these parameters for the same birds breed in different territories.

This analysis showed that about 60% of the variation in clutch size, egg size, and breeding success was attributable to bird-quality effects, whereas territory quality accounted for less than 10% of the variation in breeding success.

Magpies and song-birds

Magpies have been much in the news in Britain in recent years: their increasing abundance in urban and suburban areas has evoked some strong reactions regarding their possible effects on garden songbirds. Some city councils have even contemplated Magpie culls.

Also, the magpie killing and eating a young Blackbird “Turdus merula” while the Blackbird parents fly around frantically calling is not a pretty sight. But many of those who would happily shoot Magpies for such behavior tell of their excitement at seeing a Sparrow-hawk “Accipiter nisus” take a Starling “Sturnus vulgaris” from the bird-table.

Such double standards mean that there can be no grounds for condemning Magpies for the emotional trauma they cause bird-lovers. The real question must be whether Magpies take sufficient numbers of songbirds (adults, young, or eggs) to reduce their populations significantly. More research is required to resolve this. Though, there are several points that should be kept in mind:

(i)                 The results from the Common Birds Census (CBC) show that Magpie numbers have increased. Hence, they do not show a decrease in the numbers of Blackbirds, Song Thrushes “Turdus philomelos”, Dunnocks “Prunella modularis” or Collared Doves “Streptopelia decaocto”, are the main targets of Magpie attacks. The most CBC plots are in rural rather than suburban or urban areas, however, so we still need more information on this topic.

(ii)               The suburban song-bird populations exist at densities much greater than they do in traditional, woodland habitats;

(iii)              The ringing recoveries and other types of the study point out that the main predator of garden birds is the domestic cat. How many bird-lovers also own a cat? Virtually all the information which we have obtained on Magpies during the last few decades has been obtained through the use of color-marked individuals. These studies have been conducted primarily with rural Magpies. Hence, a similar investigation of Magpies in suburban and urban areas would provide an interesting comparison and would allow us to assess the impact of Magpies on songbirds. Clearly, we should reserve judgment on this issue until we have some hard facts.

 

Reference - British Birds VOLUME 8 2 NUMBER 12 DECEMBER 1989