Monday 21 September 2020

The white-browed robin-chat,

Heuglin’s Robin is the most wide-ranging Cossypha robin in the Afro tropical region but has only a limited distribution in the more tropical parts of southern Africa. The range extends from northern KwaZulu-Natal through Swaziland, the Transvaal Lowveld, and the Limpopo Valley, over most of Zimbabwe, and westward into the Okavango and Caprivi regions. Heuglin’s Robin is also known as white-browed robin-chat, (Cossypha heuglini) it is a species of bird in the family Muscicapidae.

It is recognized two subspecies in southern Africa: C.h. orphea with a stronghold in the Okavango and adjacent tributaries to the Zambezi River, and euro note east of this throughout the remainder of the region. Its magnificent crescendo duetting song is one of the characteristic sounds of Africa in both towns and wildlife sanctuaries.

Its white eyebrow and overall bright orange under-parts provide a unique combination that should preclude confusion with any other southern African bird, yet for many years other species have repeatedly been misidentified as Heuglin’s Robin in areas which are ecologically unsuitable and outside its range.

Habitat:

Throughout its range, it is a characteristic species of riverine forest, even where this is limited to a thin discontinuous fringe. Where it is common it also frequents evergreen thickets (as on termite mounds) in woodland and in modified areas, frequenting the gardens of homesteads and towns.

In the Transvaal and Zimbabwe, it was found most commonly (up to 3 birds/ha) in the riverine forest with a high percentage of evergreens, discontinuous canopy and well-developed shrub and ground layers. The vegetation analysis besides showing where it is most commonly encountered provides a diagrammatic representation of its decreasing abundance and smaller range from Zimbabwe southwards. From Zimbabwe northwards it is a common garden bird and may nest close to human dwellings in places such as vine-covered verandah trellises.

Movements:

It is not known to undertake regular seasonal movements anywhere within its range. The slightly lower reporting rates in winter in some regions are probably explained by quieter and more covert behavior in the nonbreeding season.

Breeding:

The bird records are showing that its breeding starts in July–May in the north and September–April further south (Zone6) with a general peak in October–November.

Eggs

Eggs are laying in usually restricted to September–January. But on a few observations have been recorded in August from Zimbabwe notwithstanding. 

Interspecific Relationships

From the eastern high lands of Zimbabwe south into the Transvaal and KwaZulu-Natal (and in many other parts of its Afrotropical range), it shares its habitat with the Natal Robin C. natalensis (Farkas1969). These species breed alongside each other and have similar diets but there is as yet no evidence of so-called competitive exclusion of either species by the other.

Historical Distribution and Conservation:

It appears to be slowly extending its established range in the south. In the 1950s its southernmost limit was that portion of the Mkuze River east of the Lebombo range (the ‘northern Zululand’ of McLachlan & Liversidge 1957). By 1970 the birds sit had reached the Hluhluwe River in the south and pushed west of the Lebombo range by way of the Pongolo and Mkuze rivers into the Louwsburg and Magut districts of KwaZulu-Natal.

However, severe damage done to the riverine forests of northern KwaZulu-Natal by Cyclone Demoina in 1987, when it has probably halted or at least set back this expansionary phase. Heuglin’s Robin is common throughout most of its widespread Afro tropical range and is not listed The IUCN classifies it as a least-concern species.

Diet

Heuglin’s Robin diet consists of many different things, like beetles, ants, termites, and some other insects, arthropods, frogs, and variable fruits. The robin likes to bathes in water.

Vocalizations

The Heuglin’s Robin contact calls include repeated pit-porlee, chiiritter-porlii and da-da-da-teee and end with da-teeee or chickle-ter-tweep. Therefore, the alarm call is takaata-kaata-kaata. The white-browed robin-chat has a melodious song, usually given at dawn and dusk, is quiet at first, and then becomes louder. It consists of many pip-pip-ureee, when singing loudly, its beak is wide open and its breast is inflated. The bird tail moves when each note is sung. Also, some observations have seen when pairs may duet.



Tuesday 1 September 2020

Starling Birds – Saints or Sinners?

Starling birds are so familiar that birdwatchers all too often ignore it. Yet, if it were as rare today as it used to be its superb iridescent plumage would rank it as one of the most beautiful of British Birds. The starling is one of our most common birds. More than six million pairs breed every year.

In the winter they are joined by at least 30 million more individuals that migrate here from northern and eastern Europe. Yet, up until the middle of the last century, the starling was relatively uncommon in Britain. The rise in the British population is part of a general pattern throughout Europe in which starlings have increased in numbers and spread westwards.

Omnivorous eaters

The reasons for this population increase is not completely understood but an important factor is the bird's ability to live on a wide variety of foods. Fruits, seeds, flying insects, caterpillars, grubs, earthworms and household waste are all eaten, although the amounts taken of these different foods vary with the season.

In spring the starling's diet consists mainly of insects and their larvae; in summer fruits become important; by winter these are replaced with seeds. Throughout the year, however, animal foods remain an important source of protein. Another reason for the starling's success is that, during the last century or so, large areas of Europe's indigenous forests have been cleared to create grassland for farming.

Habitats

Close cropped grassland is the starling's favorite habitat. One can often see those probing grassroots for invertebrates such as caterpillars, earthworms, and leatherjackets (the larvae of crane flies and a serious agricultural. During the breeding season, starlings spend most of their feeding time in grassland.

However, at other times of the year, they spread out into new habitats a necessity if they are to take full advantage of their omnivorous nature. Bushes, hedgerows, and trees are visited by starlings for fruits such as cherries, elderberries and sloes. Moreover, they also search stubble fields, newly sown cereal fields and farmyards for seeds.

Forming flocks

People often ask how starlings gather so quickly and in such numbers when food is put out into a garden. Starlings have an excellent memory, especially when it comes to remembering places where food appears regularly and in abundance. These places are always under observation by at least one bird. When food appears, one starling flies down to investigate.

If it begins to peck, then all the other starlings nearby recognize this as a sign of food and fly down to join in. Within a very short time, a feeding flock has formed. The formation of a flock for feeding is advantageous for the flock members in that they can feed much faster than when they are on their own.

There are many more eyes on the look-out for predators such as cats and sparrow hawks. Against this, however, is the problem that a flock can grow too big for the food source, with the result that bickering and fighting ensue. The starlings' An omnivorous diet means that.

Depending on what they are eating, a large flock can either inflict great damage or be of great benefit. The starlings' consumption of large numbers of leatherjackets is an obvious boon to the farmer but, on the other hand, they can devastate cherry orchards that are in fruit.

Roosting by the million

As well as feeding in flocks, starlings also roost in flocks. Some times more than a million birds gather together in night roosts, attracting large numbers of predators. In places such as Trafalgar Square, huge flocks can be seen wheeling around and darkening the sky at dusk.

Quite why starlings roost in such numbers is not yet known, but the advantages must be considerable since they outweigh the attentions of predators. It may be that roosting presents a good opportunity for poorly fed birds to learn from their better-fed neighbors the location of good food supplies.

Nesting in letterboxes

The starling's choice of nesting site shows again how well it takes advantage of opportunities presented by a man. Its most typical nest site is a natural hole, usually in a tree but also on a cliff. However, any hole of the right size and situation will do: cavities in the roofs of houses and farm buildings are especially popular, and on occasions, it even nests in letterboxes.

The breeding season begins in April. The male chooses his nest site and starts to build the nest a bulky affair of dried grasses decorated with fresh green vegetation and the petals of spring flowers. The breeding season is the only time of year when starlings are territorial.

The male defends a small territory around his nest site, but other breeding pairs are tolerated only a few yards away. Once the male has built his nest he tries to attract a female by flying inside the nest hole and singing. Once the male has a mate, she completes the nest, lining the cup with material that can range from fine grasses and feathers to string and cellophane.

Eggs and Young

Between three and six eggs may be laid, though the usual clutch is five. The eggs are small, about 3cm (1in) long, and clear pale blue or blue-green with no markings. Incubation is carried out mostly by the female and takes about 11 days. At first, the young chicks are blind and without any feathering, save for a few tufts of down.

But the chicks grow quickly since they are fed by both parents on a protein-rich diet of invertebrates; in the first 12 days their weight increases from 5g (oz) to 60g (20z). After the twelfth day they virtually cease to add weight, but their feathers begin to develop rapidly and by the time the chicks are 21 days old they are ready to leave the nest.

In most years the parents begin a second clutch of eggs. Between the first and second broods, starlings often swap partners. The female birds are moving on to join the males at the other nests. And the situation is further complicated by the fact that a few male starlings are polygamous, having two females occupying nearby nests.

Mimicry in birds

The starling's song is not particularly musical but it is remarkable for its mimicry. Sometimes it mimics phrases from the songs of neighboring starlings, but it can also mimic the calls of other birds, including bullfinches, curlews, tawny owls, and green woodpeckers. It can even imitate mammal noises-as well as inanimate sounds, such as telephones ringing.

Ornithologists have discovered that, with some species, if a male possesses a wide repertoire of songs it has a better chance of breeding successfully. This explains why starlings make such a variety of noises but not why they mimic 'foreign' sounds rather than create their own distinct sounds. That remains a mystery.

Starlings are closely related to those master-mimics, the mynah birds. Unlike the mynahs, however, starlings cannot imitate human speech. Mimicry is not confined to the starling family: parrots and jackdaws reproduce words, and many species imitate other birds.


Read More – The Curlew Bird and Its Cousin
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