Yellow-browed Warbler
Encyclopedia
The Yellow-browed Warbler (Phylloscopus inornatus) is a leaf warbler
(family
Phylloscopidae) which breeds in temperate
Asia
. This warbler
is strongly migratory
and winters mainly in tropical southeast Asia
, but also in small numbers in western Europe
. Like the rest of Phylloscopidae, it was formerly included in the Old World warbler
assemblage.
It was formerly considered to comprise of three subspecies
, but P. i. humei and P. i. mandellii are now split as a separate species, Hume's Leaf Warbler
P. humei, leaving P. inornatus monotypic
. The two sister species differ slightly but consistently in morphology
, bioacoustics
, and molecular characters. Before the species was split, the names yellow-browed willow warbler and inornate warbler were used by a few authors.
but slightly larger than Pallas's Warbler
. Like many other leaf warbler
s, it has overall greenish upperparts and white underparts. It also has prominent double wing bars formed by yellowish-white tips to the wing covert feathers (a long bar on the greater coverts and a short bar on the median coverts), yellow-margined tertial feathers, and long yellow supercilium
. Some individuals also have a faint paler green central crown stripe though many do not show this.
It is not shy, but its arboreal life style makes it difficult to observe. It is almost constantly in motion. Its song is a high pitched medley of whistles; the call is piercing, often disyllabic "tseeweest", strikingly loud for the bird's small size. The only real possibility of confusion is with the similar-looking Hume's Leaf Warbler
(P. humei), which in the limited area of overlap has duller colours, a faint second wing bar and dark legs and lower mandible. Their songs and calls are clearly distinct, with Hume's having a more chirping "chwee" call. It can easily be distinguished from Pallas's Warbler as it does not have the a conspicuous yellow central crown stripe and rump patch shown that species.
. The nest is built in dense vegetation often at the base of a tree or old stump; two to four (occasionally more) eggs are laid, hatching after 11–14 days, with the chicks fledging when 12–13 days old.
This is an abundant bird of lowland and montane
forests and woodlands; particularly in winter it may also be found in more open woods. Its breeding range extends from just west of the Ural Mountains
eastwards to eastern Siberia
, Mongolia
and northeastern China
. Its winter habitat
is lowland broadleaf or coniferous forest, from West Bengal
and Assam
in northeastern India
east through southern China
to Taiwan
, and south to the Malay Peninsula
. In summer, it occurs at altitudes of up to 2,440 m, and in winter, up to 1,525 m.
The European breeding population west of the Urals has increased westwards in recent decades; in 1950 it was described as 'fairly scarce', but 'locally abundant' with 45,000–46,000 pairs in 1990.
Small numbers, most likely from the western end of the breeding range, regularly winter in western Europe. These arrive in Great Britain
in late September and October after a 3,000–3,500 km migration from the Urals, a markedly shorter distance than the 5,500–6,000 km they would need to fly to reach the normal wintering areas in southeastern Asia. Exact numbers in this population are unknown, but typically several hundred are found arriving in Great Britain each autumn; given their unobtrusive behaviour, this is probably only a fraction of the total. In the past widely considered to be vagrants
, these birds are now thought to be undertaking a normal regular migration, able to take advantage of the mild oceanic climate
winters on the western fringes of Europe for wintering.
A common species in most of its wide range, the Yellow-browed Warbler is not considered threatened by the IUCN.
Hume's Leaf Warbler overlaps its breeding range with Yellow-browed Warbler in the western Sayan Mountains
, but the species apparently do not hybridise. Their lineages diverged roughly 2.5 million years ago.
Leaf warbler
Leaf-warblers are small insectivorous birds belonging mainly to the genus Phylloscopus. They were formerly included in the Old World warbler family but are now considered to belong to the Phylloscopidae, a family created in 2006. The genus is closely related to Seicercus and some species have been...
(family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Phylloscopidae) which breeds in temperate
Temperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...
Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
. This warbler
Warbler
There are a number of Passeriformes called "warblers". They are not particularly closely related, but share some characteristics, such as being fairly small, vocal and insectivorous....
is strongly migratory
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
and winters mainly in tropical southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...
, but also in small numbers in western Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
. Like the rest of Phylloscopidae, it was formerly included in the Old World warbler
Old World warbler
The "Old World Warblers" is the name used to describe a large group of birds formerly grouped together in the bird family Sylviidae. The family held over 400 species in over 70 genera, and were the source of much taxonomic confusion. Two families were split out initially, the cisticolas into...
assemblage.
It was formerly considered to comprise of three subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
, but P. i. humei and P. i. mandellii are now split as a separate species, Hume's Leaf Warbler
Hume's Leaf Warbler
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.This bird is named after Allan Octavian Hume...
P. humei, leaving P. inornatus monotypic
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
. The two sister species differ slightly but consistently in morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
, bioacoustics
Bioacoustics
Bioacoustics is a cross-disciplinary science that combines biology and acoustics. Usually it refers to the investigation of sound production, dispersion through elastic media, and reception in animals, including humans. This involves neurophysiological and anatomical basis of sound production and...
, and molecular characters. Before the species was split, the names yellow-browed willow warbler and inornate warbler were used by a few authors.
Description
This is one of the smaller Old World warblers, at 9.5–11 cm long and weighing 4–9 g distinctly smaller than a ChiffchaffChiffchaff
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 Asia....
but slightly larger than Pallas's Warbler
Pallas's Warbler
The Pallas's Warbler or Pallas's Leaf Warbler is a leaf warbler which breeds in southern Siberia , northern Mongolia, and northeastern China...
. Like many other leaf warbler
Leaf warbler
Leaf-warblers are small insectivorous birds belonging mainly to the genus Phylloscopus. They were formerly included in the Old World warbler family but are now considered to belong to the Phylloscopidae, a family created in 2006. The genus is closely related to Seicercus and some species have been...
s, it has overall greenish upperparts and white underparts. It also has prominent double wing bars formed by yellowish-white tips to the wing covert feathers (a long bar on the greater coverts and a short bar on the median coverts), yellow-margined tertial feathers, and long yellow supercilium
Supercilium
The supercilium is a plumage feature found on the heads of some bird species. It is a stripe which runs from the base of the bird's beak above its eye, finishing somewhere towards the rear of the bird's head. Also known as an "eyebrow", it is distinct from the eyestripe, which is a line which runs...
. Some individuals also have a faint paler green central crown stripe though many do not show this.
It is not shy, but its arboreal life style makes it difficult to observe. It is almost constantly in motion. Its song is a high pitched medley of whistles; the call is piercing, often disyllabic "tseeweest", strikingly loud for the bird's small size. The only real possibility of confusion is with the similar-looking Hume's Leaf Warbler
Hume's Leaf Warbler
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.This bird is named after Allan Octavian Hume...
(P. humei), which in the limited area of overlap has duller colours, a faint second wing bar and dark legs and lower mandible. Their songs and calls are clearly distinct, with Hume's having a more chirping "chwee" call. It can easily be distinguished from Pallas's Warbler as it does not have the a conspicuous yellow central crown stripe and rump patch shown that species.
Ecology and distribution
Like most warblers, it is insectivorousInsectivore
An insectivore is a type of carnivore with a diet that consists chiefly of insects and similar small creatures. An alternate term is entomophage, which also refers to the human practice of eating insects....
. The nest is built in dense vegetation often at the base of a tree or old stump; two to four (occasionally more) eggs are laid, hatching after 11–14 days, with the chicks fledging when 12–13 days old.
This is an abundant bird of lowland and montane
Montane
In biogeography, montane is the highland area located below the subalpine zone. Montane regions generally have cooler temperatures and often have higher rainfall than the adjacent lowland regions, and are frequently home to distinct communities of plants and animals.The term "montane" means "of the...
forests and woodlands; particularly in winter it may also be found in more open woods. Its breeding range extends from just west of the Ural Mountains
Ural Mountains
The Ural Mountains , or simply the Urals, are a mountain range that runs approximately from north to south through western Russia, from the coast of the Arctic Ocean to the Ural River and northwestern Kazakhstan. Their eastern side is usually considered the natural boundary between Europe and Asia...
eastwards to eastern Siberia
Siberia
Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...
, Mongolia
Mongolia
Mongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...
and northeastern China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
. Its winter habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
is lowland broadleaf or coniferous forest, from West Bengal
West Bengal
West Bengal is a state in the eastern region of India and is the nation's fourth-most populous. It is also the seventh-most populous sub-national entity in the world, with over 91 million inhabitants. A major agricultural producer, West Bengal is the sixth-largest contributor to India's GDP...
and Assam
Assam
Assam , also, rarely, Assam Valley and formerly the Assam Province , is a northeastern state of India and is one of the most culturally and geographically distinct regions of the country...
in northeastern India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
east through southern China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
to Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
, and south to the Malay Peninsula
Malay Peninsula
The Malay Peninsula or Thai-Malay Peninsula is a peninsula in Southeast Asia. The land mass runs approximately north-south and, at its terminus, is the southern-most point of the Asian mainland...
. In summer, it occurs at altitudes of up to 2,440 m, and in winter, up to 1,525 m.
The European breeding population west of the Urals has increased westwards in recent decades; in 1950 it was described as 'fairly scarce', but 'locally abundant' with 45,000–46,000 pairs in 1990.
Small numbers, most likely from the western end of the breeding range, regularly winter in western Europe. These arrive in Great Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
in late September and October after a 3,000–3,500 km migration from the Urals, a markedly shorter distance than the 5,500–6,000 km they would need to fly to reach the normal wintering areas in southeastern Asia. Exact numbers in this population are unknown, but typically several hundred are found arriving in Great Britain each autumn; given their unobtrusive behaviour, this is probably only a fraction of the total. In the past widely considered to be vagrants
Vagrancy (biology)
Vagrancy is a phenomenon in biology whereby individual animals appear well outside their normal range; individual animals which exhibit vagrancy are known as vagrants. The term accidental is sometimes also used...
, these birds are now thought to be undertaking a normal regular migration, able to take advantage of the mild oceanic climate
Oceanic climate
An oceanic climate, also called marine west coast climate, maritime climate, Cascadian climate and British climate for Köppen climate classification Cfb and subtropical highland for Köppen Cfb or Cwb, is a type of climate typically found along the west coasts at the middle latitudes of some of the...
winters on the western fringes of Europe for wintering.
A common species in most of its wide range, the Yellow-browed Warbler is not considered threatened by the IUCN.
Hume's Leaf Warbler overlaps its breeding range with Yellow-browed Warbler in the western Sayan Mountains
Sayan Mountains
The Sayan Mountains are a mountain range between northwestern Mongolia and southern Siberia, Russia.The Eastern Sayan extends from the Yenisei River at 92° E to the southwest end of Lake Baikal at 106° E...
, but the species apparently do not hybridise. Their lineages diverged roughly 2.5 million years ago.