Mindblowing Planet Earth

Thursday, 19 September 2019

Marsh Wren (wrens)

Order Passeriformes, Family Troglodytidae

Wrens are small insectivorous birds that live in a variety of habitats throughout the United States. They have long, slender bills adapted for gleaning insects from the ground and vegetation. Most species are migratory, although some populations are year-round residents.

Marsh Wren Facts

The marsh wren (Cistothorus palustris) is a common bird inhabiting freshwater cattail marshes and salt marshes. Marsh wrens breed throughout most of the northern half of the United States and in coastal areas as far south as Florida. In winter they are in the southern United States and into Mexico, particularly in coastal areas.

Marsh wrens eat mostly insects, and occasionally snails, which they glean from the surface of vegetation. This species was formerly known as the long-billed marsh wren (Telmatodytes palustris).

Body Size

Although wrens are small (13 cm bill tip to tail tip; about 10 g body weight), males tend to be about 10 percent heavier than females. However, the body weight varies seasonally; in Georgia, where marsh wrens are resident throughout the year, they tend to be heavier in the spring and summer than in the fall and winter.

Habitat

Marsh wrens inhabit freshwater and saltwater marshes, usually nesting in association with bulrushes, cattails, and sedges or on occasion in mangroves. Standing water from several centimeters to nearly a meter is typical of the areas selected.

However, the permanent water is necessary to provide a food supply of insects necessary to maintain the birds and as a defense against predation. Deeper water and denser vegetation are associated with reduced predation rates.

Food Habits

Marsh wrens consume aquatic invertebrates, other insects, and spiders, which they glean from the water surface, on stems and leaves of emergent vegetation, and the marsh floor. They sometimes also feed by flycatching.

The insect orders most commonly taken include Coleoptera (both adults and larvae), Diptera (adults and larvae), Hemiptera (juveniles and adults), Lepidoptera (larvae most commonly fed to nestlings); and Odonata (newly emerged).

When feeding the young, at first the parents bring mosquito adults and larvae, midges, larval tipulids, and other small insects. As the young mature, the parents bring larger insects such as ground beetles, diving beetles, long-horned beetles, caterpillars, dragonflies, and sawflies to the nestlings.

In a population in Georgia, spiders (usually 1 to 3 mm in size, sometimes 12 to 15 mm), small crabs (5 to 7 mm), small snails (1 to 3 mm), and insect eggs also were consumed and fed to nestlings. Thus, organisms that are aquatic for all or part of their lives are an important component of the diet of marsh wren adults and nestlings.

Migration

Marsh wrens are year-round residents in some southern and coastal maritime regions where marshes do not freeze. Most migratory wrens breed throughout the northern half of the United States through southern Canada and winter in Mexico and the southern half of the United States.

Breeding activities and social organization.

Many populations of marsh wren are polygynous, with some males mating with two, occasionally three, females in a season. While the remaining males have one mate or remain bachelors. In a study found 5 to 11 percent bachelor males, 41 to 48 percent monogamous males, 37 to 43 percent bigamous males, and 5 to 12 percent trigamous males in two marshes in Manitoba, Canada.

Similarly, 16 percent bachelors, 57 percent monogamous, and 25 percent bigamous males in eastern Washington state. In contrast, the most males to be monogamous through 4 years of study in Georgia.

Marsh Wren Nest

Male birds arrive at the breeding marshes before the females to establish territories that include both nest sites and foraging areas. Males build several nests in their territories throughout the breeding season. The female usually only add lining material to a nest of her choice, although some may help construct the breeding nest.

Breeding nests are oblong in shape, with a side opening, and are woven of cattails, reeds, and grasses and lashed to standing vegetation, generally 30 cm to 1 m above standing water or high tide. Incubation lasts approximately 2 weeks, as does the nestling period.

After fledging, one or both parents continue to feed the young for about 12 days. Many populations typically rear two broods per year, although some may rear three. In the more monogamous populations, both parents regularly feed young, but in the more polygynous ones, the females may provide most of the food, with males assisting only toward the end of the nestling period.

Marsh Wren Range

Marshes smaller than 0.40 ha usually are not used by breeding marsh wrens. Average male territory size for a given year and location can range from 0.006 to 0.17 ha, depending on the habitat and conditions of the year. Also, there is a trend in polygynous populations for polygynous males to defend larger territories than monogamous males or males that end up as bachelors.

Population density. Because the species is polygynous, there may be more females than males inhabiting breeding marshes. Population density varies with the suitability and patchiness of the habitat. Densities as high as 120 adult birds per hectare have been recorded.

Clutch size and number of clutches per year vary with latitude and climate. In some populations, marsh wrens commonly destroy eggs and kill the nestlings of other pairs of their own species and other marsh-nesting passerines. Fledging success depends strongly on nest location; nests over deeper water are less vulnerable to predation.

Of nests lost to all causes, it has found 44 percent due to mammalian predators, 27 percent due to other wrens, 11 percent due to weather, 8 percent due to nest abandonment, and 13 percent unknown. The annual mortality of adults is lower than that of first-year birds. Both sexes of this species usually commence breeding in the first year following hatching.

Similar species

1. The sedge wren (Cistothorus platensis, formerly known as the short-billed marsh wren) nests locally in wet meadows or shallow sedge marshes and hayfields in the northeastern United States, wintering primarily in the southeastern United States. It is slightly smaller 11 cm than the marsh wren. None of the other wren species inhabit marshes, although all forage by gleaning insects from vegetation and other surfaces. Wrens that inhabit moist woodlands and open areas are listed below.

2. The house wren (Troglodytes aedon12 cm) breeds throughout most of the United States, into southern Canada. It inhabits open habitats with brush and shrubs and is found in orchards, farmyards, and urban gardens and parks.

3. The winter wren (Troglodytes troglodytes10 cm) breeds in southern Canada, where it nests in dense brush, especially along moist coniferous woodlands. It winters primarily in the southeastern United States, where it inhabits many types of woodlands.

4. The Carolina wren (Thryothorus ludovicianus14 cm) is non-migratory and can be found in both summer and winter in the eastern United States as far north as northern Delaware and as far west as Oklahoma. It inhabits moist woodlands and swamps and wooded suburban areas.

5. Bewick's wren (Thryomanes bewickii13 cm) is more common in western States than the house wren and is declining east of the Mississippi. It is found in brushland, stream edges, and open woods.

Read More – Rubby Kingfisher / The Lesser Goldfinch (Spinus psaltria) / The Himalayan Cutia / The fire-tailed myzornis / Pando – The One Tree Forest / Great Blue Heron /

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Wednesday, 18 September 2019

Belted Kingfisher (kingfishers)

Order Coraciiformes, Family Alcedinidae

The belted kingfisher (Cerylealcyon, formerly Megaceryle alcyon) is a medium-sized bird (33 cm bill tip to tail tip) that eats primarily fish. It is one of the few species of fish-eating birds found throughout inland areas as well as coastal areas. The belted kingfisher's range includes most of the North American continent.

It breeds from northern Alaska and central Labrador southward to the southern border of the United States. Two subspecies sometimes are recognized: the eastern belted kingfisher (Ceryle alcyonalcyon), which occupies the range east of the Rocky Mountains and north to Quebec, and the western belted kingfisher (Cercyle alcyoncaurina), which occupies the remaining range to the west.

Kingfishers are stocky, short-legged birds with large heads and bills. They exist on a diet mostly of fish, which they catch by diving, from a perch or the air, headfirst into the water. They nest in burrows in earthen banks that they dig using their bills and feet.

Body Size

The belted kingfisher measures between 28 to 35 cm in length with a wingspan of between 48 to 58 cm and weigh from 113 to 178 g. The sexes are similar in size and appearance, although the female tends to be slightly larger. The western populations are somewhat larger than eastern ones. Nestlings reach adult body weight by about 16 days after hatching but then may lose some weight before fledging.

Habitat and Behavior

Belted kingfishers are typically found along rivers and streams and along lake and pond edges. They are also common on seacoasts and estuaries. They prefer waters that are free of thick vegetation that obscures the view of the water and water that is not completely overshadowed by trees.

Kingfishers also require relatively clear water to see their prey and are noticeably absent in areas when waters become turbid. That water less than 60 cm deep is preferred. They prefer stream riffles for foraging sites even when pools are more plentiful because of the concentration of fish at riffle edges. Belted kingfishers’ nest in burrows within steep earthen banks devoid of vegetation beside rivers, streams, ponds, and lakes.

They also have been found to nest in slopes created by human excavations such as roadcuts and landfills. Sandy soil banks, which are easy to excavate and provide good drainage, are preferred. In general, kingfishers’ nest near suitable fishing areas when possible but will nest away from water and feed in bodies of water other than the one closest to home.

Food Habits

Belted kingfishers generally feed on fish that swim near the surface or in shallow water. The kingfishers generally catch fish only in the upper 12 to 15 cm of the water column. Belted kingfishers capture fish by diving either from a perch overhanging the water or after hovering above the water.

Belted Kingfisher are swallowed whole, head first, after being beaten on a perch. The average length of fish is less than 7.6 cm but ranged from 2.5 to 17.8 cm. The fish caught in Ohio streams to range from 4 to 14 cm in length. Several studies indicate that belted kingfishers usually catch the prey that are most available.

Belted Kingfisher Diet

Diet, therefore, varies considerably among different water bodies and with the season. Although kingfishers feed predominantly on fish, they also sometimes consume large numbers of crayfish. However, in shortages of their preferred foods, have been known to consume crabs, mussels, lizards, frogs, toads, small snakes, turtles, insects, salamanders, newts, young birds, mice, and berries.

Belted Kingfisher Nest

Parents bring surprisingly large fish to their young. The nestlings only 7 to 10 days old were provided fish up to 10 cm long, and nestlings only 2 weeks old were provided with fish up to 13 cm in length. After fledging, young belted kingfishers fed on flying insects for their first 4 days after leaving the nest, crayfish for the next week, and by the 18th-day post-fledging, could catch fish.

Belted Kingfisher Juvenile

The juvenile plumage is maintained through the winter, and young birds undergo their first prenuptial molt in the spring between Feb and Apr. It is involving most of the body plumage. Adults have a complete postnuptial molt in the fall Aug to Oct.

Migration

This kingfisher breeds over most of the area of North America and winters in most regions of the continental United States. Although most northern kingfishers migrate to southern regions during the coldest months, some may stay in areas that remain ice-free where fishing is possible.

Breeding Activities and Social Organization

During the breeding season, pairs establish territories for nesting and fishing. Otherwise, belted kingfishers are solitary. They are not colonial nesters and will defend an unused bank if it lies within their territory. In migrating populations, the males arrive before the females to find suitable nesting territories.

Kingfishers excavate their burrows in earthen banks, forming a tunnel that averages 1 to 2 m in length, although some burrows may be as long as 3 to 4 m. The burrow entrance is usually 30 to 90 cm from the top of the bank and at least 1.5 m from the base. Burrows closer to the top may collapse, and burrows too low may flood. Burrows may be used for more than one season.

Five to seven eggs are laid on the bare substrate or on fish bones within the burrow. Only one adult, usually the female, spends the night in the nest cavity; males usually roost in nearby forested areas or heavy cover. Both parents incubate eggs and feed the young. After fledging, the young remain with their parents for 10 to 15 days.

Belted Kingfisher Range

During the breeding season, belted kingfishers require suitable nesting sites with adequate nearby fishing. During spring and early summer, both male and female belted kingfishers defend a territory that includes both their nest site and their foraging area. By autumn, each bird including the young of the year.

Belted Kingfisher defends an individual feeding territory only. The breeding territories (length of waterline protected) can be more than twice as long as the fall and winter feeding territories, and stream territories tend to be longer than those on lakes. Foraging territory size is inversely related to prey abundance.

Moreover, the population density and breeding densities of between two and six pairs per 10 km of river shoreline have been recorded, with density increasing with food availability. Kingfishers are sensitive to disturbance and usually do not nest in areas near human activity. Kingfishers typically breed in the first season after they are born.

Fledging success depends on food availability, storms, floods, predation, and the integrity of the nest burrow but can be as high as 97 percent. Dispersal of young occurs within a month of fledging.

Belted Kingfisher Call

Belted Kingfisher gives mechanical rattles, strident screams, sometimes harsh call, when threatened and flies over rivers or lakes. This is seen perched on a high snag, or hovering on quickly beating wings, then plunging headfirst into the water to grab a fish.

Similar Species

1. The green kingfisher (Chloroceryle americana) is smaller 22 cm than the belted kingfisher and is only common in the lower Rio Grande Valley. It also is found in southeastern Arizona and along the Texas coast, usually during fall and winter.

2. The ringed kingfisher (Ceryletorquata) is larger 41 cm and resides in the lower Rio Grande Valley in Texas and Mexico.

Read More – The Lesser Goldfinch (Spinus psaltria) / The Himalayan Cutia / The fire-tailed myzornis / Pando – The One Tree Forest / Great Blue Heron / Crested Kingfisher

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Tuesday, 17 September 2019

The Red-tailed Hawk Facts

Order Falconiformes, Family Accipitridae. The family Accipitridae includes most birds of prey except falcons, owls, and American vultures. Buteo hawks are moderately large soaring hawks that inhabit open or semi-open areas. They are the most common daytime avian predators on ground-dwelling vertebrates, particularly rodents and other small mammals.

They range in size from the broad-winged hawk (41 cm bill tip to tail tip) to the ferruginous hawk (58 cm). Hawks egest pellets that contain undigestible parts of their prey, such as hair and feathers, that can be useful in identifying the types of prey eaten (bones usually are digested completely).

Where Does Red-tailed Hawk Live?

The red-tailed hawk “Buteo jamaicensis” is the most common Buteo species in the United States. Breeding populations are distributed throughout most wooded and semi-wooded regions of the United States and Canada south of the tundra, although some populations are found in deserts and prairie habitats. Six subspecies are recognized. Nesting primarily in woodlands, red-tails feed in open country on a wide variety of small-to-medium-sized prey.

Body Size

Males of this medium-sized buteo (46 cm) weigh about 1 kg, and females are approximately 20 percent heavier than the males. Otherwise, the sexes look alike.

Habitat

Red-tails are found in habitats ranging from woodlands, wetlands, pastures, and prairies to deserts. They appear to prefer a mixed landscape containing old fields, wetlands, and pastures for foraging interspersed with groves of woodlands and bluffs and streamside trees for perching and nesting. Red-tails build their nests close to the tops of trees in low-density forests and often in trees that are on a slope.

In areas where trees are scarce, nests are built on other structures, occasionally in cactus, on rock pinnacles or ledges, or man-made structures. In winter, night roosts usually are in thick conifers if available and in other types of trees otherwise.

What Does Red-Tailed Hawk Eat?

The Red-tails hunt mainly from an elevated perch, often near woodland edges. Small mammals, including mice, shrews, voles, rabbits, and squirrels, are important prey, particularly during winter. Red-tails also eat a wide variety of foods depending on availability, including birds, lizards, snakes, and large insects.

In general, red-tails are opportunistic and will feed on whatever species are most abundant Winter food choices vary with snow cover; when small mammals such as voles become unavailable (under the snow), red-tails may concentrate on larger prey, such as pheasants.

Juvenile Red-tailed Hawk

Juveniles molt into adult plumage in a gradual process from the spring (age about 14 months) to summer or early fall.

Migration.

The more northerly red-tailed hawk populations are migratory while the more southerly is year-round residents.

Red-tailed Hawk Life Cycle

Red-tails lay one clutch per year consisting of one to three eggs, although a replacement clutch is possible if the initial clutch is lost early in the breeding season. Their nests are large and built of twigs. Both sexes incubate, but the male provides food for the female during incubation and the entire family following hatching. The parents continue to feed their young after fledging while they are learning to hunt.

Red-tailed Hawk Lifespan

The average life span of a wild red hawk is around 20 to 25 years.

Re-tailed Hawk Behavior

Red-tailed hawks are territorial throughout the year, including winter. Trees or other sites for nesting and perching are important requirements for breeding territories and can determine which habitats are used in an area.

Home range size can vary from a few hundred hectares to over 1,500 hectares, depending on the habitat. The size of red-tail territories and the location of boundaries between territories varied little from year to year, even though individual birds or pairs died and were replaced.

Population density.

Population densities normally do not exceed 0.03 pairs per hectare, and habitually are lower than 0.005 pairs per hectare. Populations in southern areas such as Florida can increase substantially in the winter with the influx of migrants from the more northerly populations.

Population dynamics.

Beginning at 2 years of age, most red-tailed hawks attempt to breed, although the proportion of breeding can vary by population and environmental conditions. Average clutch size varies regionally, tending to increase from east to west and from south to north. The density of their main prey, the snowshoe hare, over the years.

The mean clutch size for the red-tail population, however, appeared to vary with prey density, from 1.7 to 2.6 eggs/nest. Over the course of the study, about 50 percent of observed nestling losses occurred within 3 to 4 weeks after hatching due to starvation.

Most of the variance in yearly mortality of nestlings could be attributed to the amount of food supplied and the frequency of rain. Large raptors such as horned owls also can be important sources of mortality for red-tail nestlings in some areas.

Similar species

1. The ferruginous hawk (Buteo regalis), one of the larger buteos (58 cm), inhabits the dry open country of the western United States.

2. The red-shouldered hawk (Buteo lineatus) is slightly smaller (53 cm) and feeds on snakes, frogs, crayfish, mice, and some small birds. Its range is east of the Rocky Mountains and in California, with moist mixed woodlands preferred.

3. Swainson's hawk (Buteo swainsoni) is restricted to the open plains of the western United States. Although it is as large (53 cm) as the red-tail, it preys mostly on insects.

4. The broad-winged hawk (Buteo platypterus) is one of the smaller buteos (41 cm) and preys on mice, frogs, snakes, and insects. It prefers woodlands and is found almost exclusively east of the Mississippi River.

5. Harris' hawk (Parabuteo unicinctus) is similar in size (53 cm) to the red-tailed hawk but is restricted to the semiarid wood and brushlands of the southwest. This bird nests in saguaro, mesquite, and yucca and preys on rodents, lizards, and small birds.

6. The rough-legged hawk (Buteo lagopus) is one of the larger buteos (56 cm). It winters throughout most of the United States in open country but breeds only in the high arctic of North America.

7. The zone-tailed hawk (Buteo albonotatus) is slightly smaller (51 cm) than most buteos and feeds on rodents, lizards, fish, frogs, and small birds. It can be found in mesa and mountain country within its limited range between the southwest United States and Mexico.

8. The short-tailed hawk (Buteo brachyurus) is the smallest buteo (39 cm) and can only be found in the southern tip of Florida in mixed woodland and grassland habitats.

Read More – The Lesser Goldfinch (Spinus psaltria) / The Himalayan Cutia / The fire-tailed myzornis / Pando – The One Tree Forest / Great Blue Heron

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Thursday, 12 September 2019

American Robin Facts

The American robin (Turdus migratorius) occurs throughout most of the continental United States and Canada. This is a migratory songbird of the true thrush genus and Turdidae, the wider thrush family Muscicapidae. American robins are common garden birds overmuch of North America and their distinctive foraging behavior is well known. During the breeding season and winters in the southern half of the United States and in Mexico and Central America.

The breeding range of the robin has expanded in recent times with the increasing area covered by lawns and other open habitats. American Robin body size is approximately 23 to 28 cm long, with weight of average 77g. However, female robin is about 59 to 91g. This is commonly a friendly songbird, very much comfortable around people. Sometimes even get close to dogs while playing in yard, also fast and strong in flight. Male Robins are more aggressive then females and like to spend maximum time in interactions with fertilizable mates.

American Robin Bird

The sexes are similar in size and appearance. Their size varies slightly geographically. The smallest robins are found in the eastern United States and along the Pacific coast, and the largest ones occur in the Rocky Mountains, northern Great Plains, and northern deserts. The size of robins tends to increase with latitude in eastern North America but does not in western North America. Fledglings attain adult size at approximately 6 weeks of age.

Male Robin head differs from black to grey, with white eye arcs and white supercilia. But the throat is white with black streaks, and under tail coverts and belly are white. The bird has a brown back and a reddish-orange breast, changing from a rich red maroon to peachy orange. The bill is mostly yellow with a patchily dark tip, the dusky area becoming more widespread in winter, and the legs and feet are brownish.

Habitats

Access to fresh water, protected nesting sites, and productive foraging areas are important requirements for breeding robins. Breeding habitats include moist forests, swamps, open woodlands, orchards, parks, and lawns. Robins forage on the ground in open areas, along habitat edges, or the edges of streams.

Moreover, they also forage above ground in shrubs and within the lower branches of trees. The main threat to Juvenile robins and eggs are preyed upon by snakes, squirrels, other birds, i.e., blue jays, Steller’s Jay, scrub jays, grackles, American crows, and common ravens.

American Robin Nest

The robins mostly nest in wooded areas are usually near some type of opening such as the forest edge or a treefall gap. During the nonbreeding season, they prefer moist woods or fruit-bearing trees and shrubs. In the fall season, flocks of migratory robins are often found along forest edges or clearings where fruits are most plentiful.

American Robin Diet

The robins forage by hopping along the ground in search of ground-dwelling invertebrates and by searching for fruit and foliage-dwelling insects in shrubs and low tree branches. In the months preceding and during the breeding season, robins feed mainly on invertebrates and on some fruits.

However, during the remainder of the year, their diet consists primarily of fruits. Robins eat a wide variety of both plant and animal. The Robins don’t like to eat many seeds, so don’t try to entice with whole peanuts, mixed bird seeds, Nyjer seeds.

What Do American Robins Eat?

It is commonly eaten fruits include plums, dogwood, sumac, hackberries, blackberries, cherries, greenbriers, raspberries, and juniper. The common invertebrates include beetles, caterpillars, moths, grasshoppers, spiders, millipedes, and earthworms.

The seasonal changes in the proportion of plants and invertebrates consumed by robins in three different sections of the United States. The average occurrence of fruits of various plant families in the stomachs of robins by month for these sections. The occurrence of fruits of various plant families in more specific areas of the United States.

There are no differences between the sexes in the proportion of types of invertebrates and fruits eaten. Very young robins (up to at least 35 days of age) feed almost entirely on insects and other invertebrates. However, older juveniles tend to eat a higher proportion of fruit and easy-to-capture prey than adults.

American Robins often show food preferences: a population in central New York seemed to prefer northern arrowwood and spicebush fruits over most other plants. Moreover, in Illinois, a group ate predominantly frost grapes and Virginia creeper in the late summer and fall.

During seasons when fruits dominate the diet, robins may need to consume quantities more than their body weight to meet their metabolic needs each day. Robins, as well as other fruit-eating birds, exhibit a low digestive efficiency for fruits. It is estimated that the metabolizable energy coefficient, the proportion of food energy that is assimilated for robins eating a mixed fruit diet to be only 55 percent.

Perhaps of the low retention time of the digested matter in the gut. The short retention time might be an adaptation to eating fruit because large quantities of the fruit must be processed to obtain an adequate protein intake. In contrast, when eating insects, robins, as well as other bird species, exhibit a higher digestive efficiency of approximately 70 percent.

Moreover, the energy content of insects tends to be higher than that of most fruits, particularly on a wet weight basis. Thus, during the spring when robins are consuming insects, they should consume a smaller amount relative to their body weight than when eating fruits.

Molt

Post juvenile and post-breeding molts occur from late July to October. During this molt, robins are consuming largely fruits and other plant materials, which contain limited proteins. This may contribute to larger fruit consumption rates at this time. During the pre-breeding molt, robins are feeding primarily on insects and other invertebrates.

Migration of American Robin

Most robins nesting in the northern United States and Canada winter in the Gulf Coast States and the Carolinas. Wintering robins are most abundant between 30- and 35-degrees N latitude. Robin flocks migrate during the day, most northern robins leave their breeding grounds from September to November and return between February and April.

American Robin Song / Call

American Robin has the sweet familiar sound of spring, a string of clear whistles with a brief pause, often repeated syllables, like cheer up, cheerily, cheer up, cheerily. The male bird sings when he is in the mood to attract females. The song varies with time of the day habitually sings from a high perch in a tree. This bird sings before and after the storms, used different calls to communicate specific information to others. The Robin also alarm in a different call, when a ground predator reaches, or their nest is being directly threatened.

Breeding activities and social organization.

The onset of the breeding season is later at higher latitudes approximately 3 days for each additional degree in the east and altitudes. But mating and egg-laying generally occur in April or May. Males arrive on the breeding grounds before females to establish territories.

The female’s pair with established males, usually for the duration of the breeding season. The female primarily builds the nest out of mud, dried grass, weedy stems, and other materials constructing it on horizontal limbs, tree-branch crotches, within shrubs, or on any one of several man-made structures with horizontal surfaces.

Eggs of American Robin

First clutches usually contain 3 to 4 eggs; later clutches tend to contain fewer eggs. The female does all the incubating, which continues for 10 to 14 days following the laying of the second egg.

American Robin Nestlings

Both males and females feed the nestlings. Following fledging, the brood often divides, with the male and female each feeding half of the fledglings for another 2 weeks. Females may start another brood before the current one is independent, leaving the male to feed all the fledglings. After reaching individuality, juveniles often form foraging flocks in areas of high food availability.

Early in the breeding season, robins often roost communally. Males can continue to use these roosts throughout the breeding season. Whereas female birds stop once they begin incubating eggs. As fall approaches and their diet turns more toward fruits, robins in many areas begin to roost communally again and may join other species, such as common grackles and European starlings, in large roosts.

American Robin Nesting Habits

During the breeding season, male robins establish breeding territories, which the female helps to defend against other robins. Nonetheless, the territories of different pairs often overlap where neither pair can establish dominance. Most foraging during the breeding season is confined to the territory, but adults sometimes leave to forage in more productive areas that are shared with other individuals.

In some prime nesting areas (e.g., dense coniferous forest), where robin densities are high, territories are small, and the birds might often forage elsewhere. Adult robins often return to the same territory in succeeding years. During the nonbreeding roosting period, robins are likely to return to the same foraging sites for many weeks and to join roosts within one to three kilometers of these foraging areas.

Nesting population density varies with habitat quality. Densely forested areas that provide well-protected nest sites have been found to support high densities of nesting robins. Therefore, the relatively small territories found in these areas might not be used as much for foraging as those containing open areas.

In the nonbreeding season, robins often join single-or mixed-species roosts that can include tens of thousands of birds. Wintering robins are most common in pine or oak-pine communities of the southeastern and southcentral United States and decrease in abundance in drier, less forested areas westward.

Robins first attempt to breed the year after they hatch and will raise multiple broods in a season. Predation is often a major source of mortality for both eggs and nestlings. Approximately half of the adult birds survive from year to year. The average longevity of a robin that survives to its first January is from 1.3 to 1.4 years.

Similar Species

The wood thrush (Hylocichlamustelina), which is smaller than the robin (18 cm), co-occurs with the robin in some woodland habitats but is only present in the eastern United States. This species nests primarily in the interiors of mature forests and have been decreasing in abundance over the past decade as forested habitats in North America become increasingly fragmented. This species is also primarily a summer resident, wintering in Florida and the neotropics.

The hermit thrush (Catharusguttatus) is found in coniferous and mixed woodlands at northerly latitudes or high elevations and winters primarily in the southern half of the United States. This species is also significantly smaller (15 cm) than the robin.

Swainson's thrush (Catharusustulatus) is present in the western and northeastern United States during the summer months, wintering in the neotropics. It is also smaller than the robin (16 cm).

The varied thrush (Ixoreus naevius) occurs in moist coniferous forests of the Pacific Northwest. This bird is similar in size (21 cm) to the robin.

Moreover, the thrushes are common, medium-sized birds that eat worms, insects, and fruit. They live in a variety of habitats, including woodlands, swamps, suburbs, and parks. Most thrushes build nests of mud and vegetation on the ground or in the crotches of trees or shrubs; bluebirds’ nest in holes in trees and posts or in nest boxes.

This group forages primarily on the ground and in low vegetation by probing and gleaning. Some thrushes are neotropical migrants while others reside year-round in North America. Thrushes range in size from the eastern and western bluebirds (18 cm from bill tip to tail tip) to the American robin (23cm to 25 cm). Male and female plumages are similar in most thrushes, although in some species, such as the bluebirds, the males are more brightly colored.

Read More – The Lesser Goldfinch (Spinus psaltria) / The Himalayan Cutia / The fire-tailed myzornis / Pando – The One Tree Forest / Great Blue Heron

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