Wednesday, 9 May 2018
9-5-2018 RACO DE OLLA, VALENCIA - PIED AVOCET (Recurvirostra avosetta)
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The pied avocet (Recurvirostra avosetta) is a large black and white wader in the avocet and stilt family, Recurvirostridae. They breed in temperate Europe and across the Palearctic to Central Asia then on to the Russian Far East. It is a migratory species and most winter in Africa or southern Asia. Some remain to winter in the mildest parts of their range, for example in southern Spain and southern England. The pied avocet is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.
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The pied avocet was one of the many bird species originally described by Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae, where it was given the binomial name of Recurvirostra avosetta. This species gets its English and scientific names from the Venetian word avosetta. It appeared first in Ulisse Aldrovandi's Ornithologia (1603). While the name may refer to black and white outfits once worn by European advocates or lawyers, the actual etymology is uncertain. Other common names include black-capped avocet, Eurasian avocet or just avocet.
It is one of four species of avocet that make up the genus Recurvirostra. The genus name is from Latin recurvus, "curved backwards" and rostrum, "bill". A 2004 study combining genetics and morphology showed that it was the most divergent species in the genus.
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The pied avocet is a striking white wader with bold black markings. Adults have white plumage except for a black cap and black patches in the wings and on the back. They have long, upturned bills and long, bluish legs. It is approximately 16.5–17.75 in (41.9–45.1 cm) in length of which the bill is approximately 2.95–3.35 in (7.5–8.5 cm) and the legs are approximately 3–4 in (7.6–10.2 cm). Its wingspan is approximately 30–31.5 in (76–80 cm). Males and females look alike. The juvenile resembles the adult but with more greyish and sepia tones.
The call of the avocet is a far-carrying, liquid, melodious kluit kluit.
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These birds forage in shallow brackish water or on mud flats, often scything their bills from side to side in water (a feeding technique that is unique to the avocets). They mainly eat crustaceans and insects.
Their breeding habitat is shallow lakes with brackish water and exposed bare mud. They nest on open ground, often in small groups, sometimes with other waders. Three to five eggs are laid in a lined scrape or on a mound of vegetation.
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9-5-2018 DEVESA, VALENCIA - BLACK TAILED GODWIT (limosa limosa)
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The black-tailed godwit (Limosa limosa) is a large, long-legged, long-billed shorebird first described by Carl Linnaeus in 1758. It is a member of the godwit genus, Limosa. There are four subspecies, all with orange head, neck and chest in breeding plumage and dull grey-brown winter coloration, and distinctive black and white wingbar at all times.
Its breeding range stretches from Iceland through Europe and areas of central Asia. Black-tailed godwits spend (the northern hemisphere) winter in areas as diverse as the Indian subcontinent, Australia, New Zealand, western Europe and west Africa. The species breeds in fens, lake edges, damp meadows, moorlands and bogs and uses estuaries, swamps and floods in (the northern hemisphere) winter; it is more likely to be found inland and on freshwater than the similar bar-tailed godwit. The world population is estimated to be 634,000 to 805,000 birds and is classified as Near Threatened. The black-tailed godwit is the national bird of the Netherlands.
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The black-tailed godwit was formally described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae under the binomial name Scolopax limosa. It is now placed with three other godwits in the genus Limosa that was introduced by the French zoologist Mathurin Jacques Brisson in 1760. The name Limosa is from Latin and means "muddy", from limus, "mud". The English name "godwit" was first recorded in about 1416–17 and is believed to imitate the bird's call.
Four subspecies are recognised:
L. l. islandica – Brehm, 1831: the Icelandic black-tailed godwit, which breeds mostly in Iceland, but also on the Faeroe Islands, the Shetland and the Lofoten Islands. It has a shorter bill, shorter legs and more rufous coloration extending onto the belly, compared to limosa.
L. l. limosa – (Linnaeus, 1758): the European black-tailed godwit, which breeds from western and central Europe to central Asia and Asiatic Russia, as far east as the Yenisei River. Its head, neck and chest are pale orange.
L. l. melanuroides – Gould, 1846: the Asian black-tailed godwit, which breeds in Mongolia, northern China, Siberia and Far Eastern Russia. Its plumage is similar to islandica, but the bird is distinctly smaller.
L. l. bohaii – Zhu, Piersma, Verkuil & Conklin, 2020:[10] assumed to breed in Russian Far East; non-breeding in northeast China, Hong Kong, Vietnam, Peninsular Malaysia
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The black-tailed godwit is a large wader with long bill (7.5 to 12 cm (3.0 to 4.7 in) long), neck and legs. During the breeding season, the bill has a yellowish or orange-pink base and dark tip; the base is pink in winter. The legs are dark grey, brown or black. The sexes are similar, but in breeding plumage, they can be separated by the male's brighter, more extensive orange breast, neck and head. In winter, adult black-tailed godwits have a uniform brown-grey breast and upperparts (in contrast to the bar-tailed godwit's streaked back). Juveniles have a pale orange wash to the neck and breast.
In flight, its bold black and white wings and white rump can be seen readily. When on the ground it can be difficult to separate from the similar bar-tailed Godwit, but the black-tailed godwit's longer, straighter bill and longer legs are diagnostic. Black-tailed godwits are similar in body size and shape to bar-taileds, but stand taller.
It measures 42 cm (17 in) from bill to tail with a wingspan of 70–82 cm (28–32 in). Males weight around 280 g (9.9 oz) and females 340 g (12 oz).[12] The female is around 5% larger than the male,[8] with a bill 12–15% longer.
The most common call is a strident weeka weeka weeka.
A study of black-tailed godwits in the Netherlands found a mortality rate of 37.6% in the first year of life, 32% in the second year, and 36.9% thereafter.
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Black-tailed godwits have a discontinuous breeding range stretching from Iceland to the far east of Russia. Their breeding habitat is river valley fens, floods at the edges of large lakes, damp steppes, raised bogs and moorlands. An important proportion of the European population now uses secondary habitats: lowland wet grasslands, coastal grazing marshes, pastures, wet areas near fishponds or sewage works, and saline lagoons. Breeding can also take place in sugar beet, potato and rye fields in the Netherlands and Germany.
In spring, black-tailed godwits feed largely in grasslands, moving to muddy estuaries after breeding and for winter. On African wintering grounds, swamps, floods and irrigated paddy fields can attract flocks of birds. In India, inland pools, lakes and marshes are used, and occasionally brackish lakes, tidal creeks and estuaries.
Godwits from the Icelandic population winter mainly in the United Kingdom, Ireland, France and the Netherlands, though some fly on to Spain, Portugal and perhaps Morocco. Birds of the limosa subspecies from western Europe fly south to Morocco and then on to Senegal and Guinea-Bissau. Birds from the eastern European populations migrate to Tunisia and Algeria, then on to Mali or Chad. Young birds from the European populations stay on in Africa after their first winter and return to Europe at the age of two years. Asian black-tailed godwits winter in Australia, Taiwan, the Philippines, Indonesia, and Papua New Guinea.
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Black-tailed godwits are much more likely to be found on inland wetlands than the more coastal bar-tailed godwit. They migrate in flocks to western Europe, Africa, south Asia and Australia. Although this species occurs in Ireland and Great Britain all year-round, they are not the same birds. The breeding birds depart in autumn, but are replaced in winter by the larger Icelandic race. These birds occasionally appear in the Aleutian Islands and, rarely, on the Atlantic coast of North America.
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Black-tailed godwits are mostly monogamous; although it was not recorded in a four-year study of 50–60 pairs, bigamy was considered "probably frequent". A study of the Icelandic population showed that despite spending winter apart, pairs are reunited on their breeding grounds within an average of three days of each other. If one partner does not arrive on time, 'divorce' occurs. They nest in loose colonies. Unpaired males defend a temporary territory and perform display flights to attract a mate. Several nest scrapes are made away from the courtship territory, and are defended from other godwits. Once eggs are laid, an area of 30–50 m (98–164 ft) around the nest is defended. The nest is a shallow scrape on the ground, usually in short vegetation. The eggs may be hidden with vegetation by the incubating parent.
The single brood of three to six eggs, coloured olive-green to dark brown, measure 55 mm × 37 mm (2.2 in × 1.5 in) and weigh 39 g (1.4 oz) each (of which 6% is shell). Incubation lasts 22–24 days and is performed by both parents. The young are downy and precocial and are brooded while they are small and at night during colder weather. After hatching, they are led away from the nest and may move to habitats such as sewage farms, lake edges, marshes and mudflats. The chicks fledge after 25–30 days.
Black-tailed godwit productivity varies, positively, with spring temperatures. However, during extreme events, such as a volcanic eruption, complete breeding failures can occur.
They mainly eat invertebrates, but also aquatic plants in winter and on migration. In the breeding season, prey includes beetles, flies, grasshoppers, dragonflies, mayflies, caterpillars, annelid worms and molluscs. Occasionally, fish eggs, frogspawn and tadpoles are eaten. In water, the most common feeding method is to probe vigorously, up to 36 times per minute, and often with the head completely submerged. On land, black-tailed godwits probe into soft ground and also pick prey items from the surface.
Tuesday, 8 May 2018
15-4-2018 CHOBE RIVER, NAMIBIA - AFRICAN STONECHAT (Saxicola torquatus) COURTESY OF MRS VALERIE FISHER
The males have a black head, a white half-collar, a black back, a white rump, and a black tail; the wings are black with a large white patch on the top side of the inner wing. The upper breast is usually dark orange-red, with a sharp or gradual transition to white or pale orange on the lower breast and belly depending on subspecies. In a few, black replaces the orange breast feathers in part or entirely.
Females have brown rather than black above and on the head with an indistinct paler eyebrow line, chestnut-buff rather than orange below, and less white on the wings. Both sexes' plumage is somewhat duller and streakier outside the breeding season.
It has a scattered distribution across much of sub-Saharan Africa, occurring locally as far north as Senegal and Ethiopia. Outlying populations are found the mountains of southwest Arabia and on Madagascar and Grande Comore. It is non-migratory, moving only locally if at all. As a result, it has developed much regional variation, being divided into 13 subspecies.
Monday, 7 May 2018
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