singing its monotonous chip-chip-chip song from the top of a spiky
spruce, this Chinese Leaf-Warbler (left) typifies the family. It
is a small, plain, rather drab but restless little bird whose vocalizations
make it much easier to identify than anything in its plumage. As it happens,
Chinese Leaf-Warbler is a newly described species, discovered and split
from the Pallas's/Lemon-rumped Warbler group on the basis of its distinctive
song and calls (Alström, Olsson & Colston 1992). It breeds in
a few forested mountains outside of Beijing; its winter range and migration
routes are virtually unknown because it is almost impossible to identify
when silent. It was initially named Phylloscopus sichuanensis (Alström
et al. 1992) but recent evidence shows that the older yunnanensis
has priority (Dickinson 2003). There has been a history of nothing but
confusion about this tiny bird!
The Leaf-Warblers are a branch of "Old World Warblers," one of 10 or more branches that sprouted as Families with the break-up of the Sylviidae [see a discussion of the Break-Up of the Old World Warblers]. Alström et al. (2006) formally proposed the name Phylloscopidae for "clade F" in their biochemical study of the Sylviodea superfamily. They and others (e.g., Jønsson & Fjeldså 2006, Barker et al. 2004) have shown this is a distinctive lineage but the exact parameters of it are not yet known. It includes birds currently assigned to genera Phylloscopus and Seicercus [the latter is embedded within the current species assigned to Phylloscopus, so there will be generic changes in the future.]
Phylloscopidae is comprised of many small tree-loving warblers. Many are
canopy or sub-canopy species, gleaning insects from leaves. Many are long-distance
migrants. Many are also rather plain little birds — in muted tones of green,
yellow, or brown — and identification can be difficult. One very widespread
species is Common Chiffchaff (right, in a nice shot by Blake Matheson).
It has a nice onomatipedic name for its breeding season song. The identification
of Phylloscopus warblers — birders tend to call them "Phylloscs"
— has been the subject of much Holarctic literature. Some of the classic
older works are Ticehurst (1938) and Williamson (1976); material on more
specific species includes that by Dean (1985) and Madge (1987).
The exact parameters of the Phylloscopidae is not yet known. There are
at least 56 species that are currently assigned to the genus Phylloscopus,
and another 12 assigned to Seicercus which, as noted above, is embedded
within Phylloscopus from a biochemical standpoint. Our headline
species — Chinese Leaf-Warbler (above) — is a Phylloscopus, one
of several recently described species (e.g., Alström et al. 1992,
1997). So a whole lot of this family is composed of these leaf-warblers.
Dickinson (2003) has a subfamily "Phylloscopinae" that might suggest the
limits of this group, but it includes a variety of genera that proved not
to be related. For example, both the monotypic genus Tickellia (Broad-billed
Warbler) and the 3 species in Abroscopus proved to be members of
the Cettiidae. All of the Phylloscopidae breed exclusively in the Old World,
except for Arctic Warbler
Phylloscopus borealis, whose range extends
across the Bering Strait into northern Alaska.
are many species breeding at temperate and high latitudes in Eurasia that
migrate substantial distances to winter in southeast Asia, India, or Africa.
One of these in Tickell's Warbler (right). It breeds in scrub at
high elevation in the Himalayas and on the Tibetan Plateau and then moves
downslope and south to winter in the Himalayan foothills of India and Burma.
It is an extremely active little warbler, and I rather shocked myself in
obtaining this digiscoped image.
The long distances traveled by Phylloscopus warblers present
much opportunity for migratory mistakes and vagrancy. A few such birds
will go the "wrong way" and become vagrants to western North America. I
refuted one claim years ago ("Willow Warbler;" Roberson & Pitelka 1983)
but recently an actual Willow Warbler was found as a vagrant in Alaska.
I've had the good fortune to see both Arctic P. borealis and Dusky
fuscatus warblers in California.
Photos: The Chinese Leaf-Warbler Phylloscopus yunnanensis was singing at the top of a spruce at Wulsingham, Hebei Province, China, in June 2004. Blake Matheson photographed the Common Chiffchaff P. collybita at El Hondo, Valencia, Spain, on 14 Mar 2005. The Tickell's Warbler P. affinis was on breeding territory in Huzu Bei Shan Nat'l Park, Qinghai Province, China, in June 2004. All photos © 2006 Don Roberson, execpt the photo attributed to Blake Matheson, used with permission; all rights reserved.
There is no "family book" covering the Leaf-Warblers so information must be sought in a variety of texts. The next volume of HBW will cover all the sylvioid warblers.
Alström, P., U. Olsson, and P.R. Colston. 1992. A new species of Phylloscopus warbler from central China. Ibis 134: 329-334.
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