Pallas's leaf warbler

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Pallas's leaf warbler
20070304Gui Yang -Huang Yao Liu Ying .jpg
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Phylloscopidae
Genus: Phylloscopus
Species:
P. proregulus
Binomial name
Phylloscopus proregulus
(Pallas, 1811)
PhylloscopusProregulusIUCN.svg
Range of P. proregulus
  Breeding
  Passage
  Non-breeding

Pallas's leaf warbler (Phylloscopus proregulus) or Pallas's warbler, is a bird that breeds in mountain forests from southern Siberia east to northern Mongolia and northeast China. It is named for German zoologist Peter Simon Pallas, who first formally described it. This leaf warbler is strongly migratory, wintering mainly in south China and adjacent areas of southeast Asia, although in recent decades increasing numbers have been found in Europe in autumn.

Contents

Pallas's leaf warbler is one of the smallest Palearctic warblers, with a relatively large head and short tail. It has greenish upperparts and white underparts, a lemon-yellow rump, and yellow double wingbars, supercilia and central crown stripe. It is similar in appearance to several other Asian warblers, including some that were formerly considered to be its subspecies, although its distinctive vocalisations aid identification.

The female builds a cup nest in a tree or bush, and incubates the four to six eggs, which hatch after 12–13 days. The chicks are fed mainly by the female and fledge when they are 12–14 days old; both parents then bring food for about a week. Pallas's leaf warbler is insectivorous, feeding on the adults, larvae and pupa of small insects and spiders. Birds forage in bushes and trees, picking items from leaves or catching prey in short flights or while hovering. The Pallas's leaf warbler has a large range, and its numbers are believed to be stable. It therefore is evaluated as of "least concern" by the International Union for Conservation of Nature (IUCN).

Taxonomy

The English name of Pallas's leaf warbler commemorates the German zoologist Peter Simon Pallas, who found it on the Ingoda River in Siberia in May 1772. [lower-alpha 1] He named the new species as Motacilla proregulus when he finally published his findings in 1811. [3] The current genus name Phylloscopus is from Ancient Greek phullon, "leaf", and skopos, "seeker" (from skopeo, "to watch"). The specific proregulus is from Greek pro, "close to", and the name regulus, referring to the similar-looking goldcrest, Regulus regulus. [4]

First described by German zoologist Friedrich Boie in 1826, the genus Phylloscopus comprises about 50 species of small insectivorous Old World woodland warblers that are either greenish or brown above and yellowish, white or buff below. The genus was formerly part of the Old World warbler family Sylvidae, but has now been split off as a separate family, the Phylloscopidae. [5]

Within the genus, Pallas's leaf warbler is one of a group of similar tiny Asiatic species characterised by a yellow rump, a strong supercilium (stripe over the eye), double wing bars and a stripe on the crown of the head, [6] once separated as the genus Abrornis but currently retained in Phylloscopus. [7] [8]

Pallas's leaf warbler was itself formerly treated as a complex of several subspecies, with the nominate form P. p. proregulus breeding in northern Asia, and other subspecies breeding much further south at high altitudes in the mountains from the western Himalayas east to western China (Yunnan and north to Gansu and Hebei). [9] [10]

Although nineteenth-century field naturalists such as Gilbert White and William Edwin Brooks had noted the importance of calls in separating often very similar-looking leaf warblers, [11] [12] for many years their views were not always accepted by the ornithological establishment. [13] More recently, vocalisations have become increasingly important in taxonomy. In the case of the former subspecies of Pallas's leaf warbler, even though they differ only slightly in plumage, the southern forms are very distinctive vocally. Their songs and calls differ from those of the nominate race, and DNA analysis from 2006 has confirmed these forms to be sufficiently distinct that they are now treated as separate species, leaving Pallas's leaf warbler as a monotypic taxon. The split species are: [10] [14] [15]

Of these, Phylloscopus chloronotus forresti is possibly also a separate species, but further analysis is required to confirm this. The breeding ranges of the Gansu leaf warbler and the Chinese leaf warbler overlap in southern Gansu, but the species are separated ecologically: the Gansu leaf warbler is found in taller forest habitats and the Chinese leaf warbler uses lower, often scrubby habitats. [10] "Lemon-rumped warbler" was sometimes used as synonym for Pallas's leaf warbler before the species' split. [16] Pallas's leaf warbler appears to have diverged from the Chinese leaf warbler 4.1–5.5 million years ago, and from its other former subspecies about 1.7–3.2 million years ago. [15]

Description

Showing head stripes Pallas's Leaf-Warbler - great rarity in Italy S4E1751 (19261546342).jpg
Showing head stripes

Pallas's leaf warbler is one of the smallest warblers, with a large head and short tail. [17] At 9–10 centimetres (3.5–3.9 in) long and 4–7 grams (0.14–0.25 oz) in weight, it is slightly smaller than a yellow-browed warbler and barely any larger than a goldcrest. It has greenish upperparts and white underparts, but is very striking, with prominent pale yellow double wingbars on the wing covert feathers, bold yellow supercilia and central crown stripe, and a lemon-yellow rump. [17] [18] The bill is blackish-brown with a yellowish tinge to the cutting edges and the base of the lower mandible, the iris is brown, and the legs are brown with a green or greyish tinge. [16] Although the yellow rump is obvious when a bird is low in vegetation or hovering, it can otherwise be hard to see. [17]

In Asia, Pallas's leaf warbler can be distinguished from its former subspecies by its yellower head stripes, wingbars and throat as well as its different vocalisations. [18] Other yellow-rumped Asiatic warblers resemble Pallas's; buff-barred and Brooks's leaf warblers are larger, much duller green above and less strongly marked, and their wing bars are buff and white respectively, not yellow. Ashy-throated warbler has grey head markings, face and throat, and pale yellow underparts. [16]

The sexes of Pallas's leaf warbler have similar plumage, but non-breeding birds are somewhat brighter green above and have broad, bright fringes to their flight feathers. Juveniles are like the adults, but have a brown tinge to the upperparts, greyish-white underparts and a duller supercilium. Adults have a complete post-breeding moult in August or September before migrating south. Juveniles and pre-breeding adults have a partial moult in March or April, replacing all the body plumage and some tail feathers. [16]

The song of Pallas's leaf warbler is delivered from a concealed perch near the top of a tall tree. [19] It is strong and prolonged, with a medley of whistles, tirrit-tirrt-tirrit-terchee-choo-choo-chee-chee-chee or similar, with some phrases reminiscent of a canary, and interspersed trills. It lasts 2–4 seconds and may be heard in the winter quarters as well as from breeding birds. [20] The call is a short, soft dju-ee. [16] In contrast, the former subspecies have quite different songs, with sustained rattles for several seconds, or sometimes minutes. Their calls are typically sharp and monosyllabic. [21] [22]

Distribution and habitat

Siberian taiga woodland Pinega Krasnaya gorka.JPG
Siberian taiga woodland

Pallas's leaf warbler breeds in coniferous taiga forests including fir, spruce, pine and larch, or in mixed forest with rhododendron, karsu oak and a high percentage of conifers. In southern Russia, it was found breeding at up to 1,500–1,700 metres (4,900–5,600 ft). In winter, it uses a wider range of habitats, including broadleaf forest and scrub as well as conifers, and can be found in river valleys down to 100 metres (330 ft). [16] [18]

Pallas's leaf warbler breeds in Siberia from the Altai Mountains east to the Sea of Okhotsk, northern Mongolia, northeast China and possibly North Korea. It is strongly migratory and winters mainly in subtropical south China, northern Thailand and elsewhere in northeastern Indochina. [18] It is rare but annual in Japan. [19]

Other movements

From John Gould's 1837 illustration of "Dalmatian Regulus" Dalmatian regulus gould.jpg
From John Gould's 1837 illustration of "Dalmatian Regulus"

Pallas's leaf warbler now occurs regularly in Europe in autumn. The first known European record was shot in 1829 in Dalmatia, now Croatia, but John Gould, who formally described it, did not realise the species had already been discovered in Asia, and named it as the "Dalmatian Regulus", Regulus modestus. [24] German ornithologist Heinrich Gätke, who moved to the then-British island of Heligoland in 1837 and stayed there for some fifty years, subsequently showed that several Asiatic species, including an occasional Pallas's leaf warbler, were regularly found there in autumn. [25] [26]

In the far west of Europe, the UK's first Pallas's leaf warbler was shot in 1896, [27] although it was not until 1951 that the second was found. [28] Thereafter, this species became increasingly common, ceasing to be a national rarity at the end of 1990. [29] In 2003, for example, 313 were recorded in Britain. [30] Pallas's leaf warbler also occurs at least annually in Sweden, Finland and Denmark. [31]

Most Pallas's leaf warblers found in Europe are first-year birds, [31] and several reasons for the large increase in numbers in autumn have been proposed. In the past, these warblers were widely considered to be vagrants or reverse migrants, but were more recently thought to be undertaking a regular migration, taking advantage of the mild oceanic climate on the western fringes of Europe for overwintering. [32] A flaw in that theory is that many birds should winter in Spain, particularly in the northwest, but Pallas's leaf warbler is rare in that country and tends to occur in the east. Spanish ornithologist Eduardo de Juana has therefore proposed that once the warblers reach northwest Europe, they then reorientate to a south easterly direction. [33]

Outside Europe, Pallas's leaf warbler has been recorded as a vagrant in north Africa (Tunisia [1] and Morocco), western Asia (Israel, Turkey and Iran), central Asia (Uzbekistan and Tajikistan), southeast Asia (Bangladesh and Taiwan), and Alaska. [18]

Behaviour

Pallas's leaf warbler is not wary but its unobtrusive arboreal lifestyle makes it difficult to observe, particularly in thick foliage. It is constantly in motion, and often hovers briefly like a goldcrest, although more frequently, [20] and may sometimes hang upside-down. [17]

Breeding

Nesting is from June to July, with eggs laid from mid-June. The nest is built by the female in a conifer, usually next to the trunk at 0.5–10 metres (1.6–32.8 ft) above ground, sometimes in a bush. It is a round or elliptical cup made from twigs, leaves and other vegetation and lined with finer material including feathers, hair or fine grasses. [18] Four to six blue-grey flecked white eggs are laid and incubated by the female. [34] They hatch after 12–13 days, with the chicks fledging when 12–14 days old. They are fed mainly by the female while in the nest, but by both parents for about a week after fledging. In the south of the range, a pair may sometimes raise a second brood. The breeding territory in central Siberia is usually 3–5 hectares (7.4–12.4 acres), infrequently as much as 10 hectares (25 acres). [18]

Pallas's leaf warbler, as with other members of its genus, is a host of the oriental cuckoo, a brood parasite. [35] The cuckoo's egg is similar in appearance, though larger, to those of the host species. [34]

Feeding

Like its relatives, Pallas's leaf warbler is insectivorous, feeding on the adults, larvae and pupa of small insects including flies, moths and aphids; spiders are also taken. Birds forage in bushes and trees, picking items from leaves or catching prey in short flights or while hovering. When not breeding, they may join mixed-species foraging flocks together with tits, goldcrests and other warblers. [18] [20] In Asia, accompanying species may also include white-eyes, minivets and babblers. [36]

Status

The Pallas's leaf warbler has a large range, and although global population trends have not been quantified, numbers are believed to be stable. This species does not approach the thresholds for the population decline criterion of the IUCN Red List (that is, declining more than 30 percent in ten years or three generations). For these reasons, it is evaluated as of "least concern" by the IUCN. [1]

Pallas's leaf warbler is widespread, common and locally abundant in Russia and northeast China. Breeding densities of up to 35–50 pairs/km2 (90–130 pairs/mi2) have been recorded in southeast Russia, with only slightly lower figures in Siberia. It is locally common in parts of its wintering grounds in southeast Asia. [18]

Notes

  1. Pallas led a scientific expedition to Siberia, sponsored by Catherine the Great, between 1768 and 1774. [2]
  2. Gould did the preliminary sketch, and his wife Elizabeth completed the detailed final painting. [23]

Related Research Articles

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Common chiffchaff Small migratory passerine bird found in Europe, Asia and north Africa

The common chiffchaff, or simply the chiffchaff, is a common and widespread leaf warbler which breeds in open woodlands throughout northern and temperate Europe and the Palearctic.

Iberian chiffchaff Species of bird

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Willow warbler Species of bird

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Greenish warbler Species of bird

The greenish warbler is a widespread leaf warbler with a breeding range in northeastern Europe, and temperate to subtropical continental Asia. This warbler is strongly migratory and winters in India. It is not uncommon as a spring or early autumn vagrant in Western Europe and is annually seen in Great Britain. In Central Europe large numbers of vagrant birds are encountered in some years; some of these may stay to breed, as a handful of pairs does each year in Germany.

Yellow-browed warbler Species of bird

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Goldcrest Small passerine bird in the kinglet family

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Humes leaf warbler Species of bird

Hume's leaf warbler or Hume's warbler is a small leaf warbler which breeds in the mountains of inner Asia. This warbler is migratory and winters mainly in India.

Pallass grasshopper warbler Species of bird

Pallas's grasshopper warbler, also known as the rusty-rumped warbler, is an Old World warbler in the grass warbler genus Helopsaltes. It breeds in the east Palearctic - Siberia to Manchuria and Sea of Japan, NE China, Altai Mountains, Sayan Mountains and Transbaikalia Sea of Okhotsk and Kamchatka. It is migratory, wintering from India east to Indonesia, where it is a rare migrant in Sri Lanka.

Raddes warbler Species of bird

Radde's warbler is a leaf warbler which breeds in Siberia. This warbler is strongly migratory and winters in Southeast Asia. The genus name Phylloscopus is from Ancient Greek phullon, "leaf", and skopos, "seeker". The specific schwarzi commemorates German astronomer Ludwig Schwarz (1822–1894).

Madeira firecrest Very small passerine bird in the kinglet family from Madeira

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Siberian accentor Small passerine bird that breeds in northern Russia

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Gansu leaf warbler Species of bird

The Gansu leaf warbler is a small passerine bird known only from China. It belongs to the leaf warbler genus Phylloscopus within the family Phylloscopidae. It was formerly treated as a subspecies of Pallas's warbler but is now regarded as a separate species based on differences in voice and cytochrome-b gene sequences.

Chinese leaf warbler Species of bird

The Chinese leaf warbler is a species of Old World warbler in the family Phylloscopidae. Its natural habitats are subtropical or tropical dry forests and subtropical or tropical high-altitude shrubland. It is found only in China.

White-spectacled warbler Species of bird

The white-spectacled warbler is a species of leaf warbler in the family Phylloscopidae. It is found in Asia from the eastern Himalayas to south-eastern China and southern Vietnam. Its natural habitats are subtropical or tropical moist lowland forests and subtropical or tropical moist montane forests. It was formerly included in the Old World warbler family, Sylviidae.

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Cited texts

Further reading