 The
"Old World Warbler," when assigned to the family Sylviidae, once included
~400 species, the largest family in the world but for the Tyrant Flycatchers
of the New World (~425 species). New biochemical information has shown
that this huge "Old World Warbler" assemblage actually represents 10 or
more different major lineages; Alström et al. (2006), Jønsson
& Fjeldså (2006), Barker et al. 2004. The inevitable process
of breaking them up into new families and proposing Family names for several
of the lineages began with Alström et al. (2006); see a discussion
of the Break-up
of the Old World Warblers for more details. They also left many other
decisions for the future.
Among the interesting findings derived from DNA biochemical research is that the Sylvia warblers — the first Old World warblers named to science and the base name of the family — are actually more closely related to babblers than they are to most of the other Old World warblers. The Sardinian Warbler (left, in a beautiful shot by Blake Matheson), found around the Mediterranean, is one of ~18 species of Sylvia found primarily in Europe, north Africa, and the Middle East. They are mostly skulking birds of the undergrowth — recalling many babblers in this respect — that are often best seen when sitting up singing and defending territories. Other well known Sylvia warblers include the Blackcap S. atricapilla, several species of Whitethroat, and the Dartford Warbler S. undata of Europe, which reaches southern England and is an inhabitant of dense heath. |
||
 Closely
related are five species in the genus Parisoma on the Arabian Peninsula
and in Africa. Indeed, this genus appear to be embedded within Sylvia
(see Shirihai et al. 2001) and should all be merged into Sylvia.
One of these is Chestnut-vented Warbler P., er, S.
subcaeruleum of arid scrub in southwestern Africa (right). You can
see its preferred thornscrub in the photo.
Jønsson & Fjeldså (2006) have reviewed all recent biochemical studies involving the oscine passerines, the largest group of birds in the world. They confirm that the oscine passerines are divided into two major groups — the Corvida (and allies) and Passerida — and that the latter are represented by, setting aside various early branches such as Rockfowl and some other oddities (e.g., Hyliotas in Africa, Kinglets in the Holarctic), three distinct major "limbs" on the passerine supertree: the Passerodiea, Muscicapoidea, and Sylviodea. Each of these three "limbs" has "branches," termed "clades," which represent significant evolutionary lineages. Within the Sylviodea they describe 13 such "clades." Some of these seem obvious enough — for example, all the swallows fall into "clade 6" and all the larks fall into "clade 3" — but others are much less apparent. Birds once assigned to "Old World Warblers" appear in six different "clades" and even within "clades" there are obviously distinctive lineages, like the Long-tailed Tits. The final two "clades" in the Sylvoidae are "clades" 12 and 13. The Sylvia warblers are in "clade 12" and that is the "clade" that I designate as a Family here. However, most recent researchers combine "clades" 12 & 13 into one huge Babbler assemblage (e.g., Barker et al. 2004). Alström et al. (2006) even proposed that the Family name Timaliidae — the current name for the Babbler family — be used for the all the birds in this assemblage. They also suggest that the name "Sylviidae" be suppressed, a decision that can only be taken by the International Commission on Zoological Nomenclature. It seems possible that the lineages in the separate "clade 12" and "clade 13" should each have their own Family name, rather than be lumped in one huge Babbler melting-pot. Until this is better sorted out, I use the name 'Sylviidae' for "clade 12" of Jønsson & Fjeldså (2006), and restrict it to the group of birds discussed on this page: the Sylvia warblers, certain related babblers, most of the parrotbills, and Wrentit. Readers should understand this is simply a personal — and likely temporary — resolution to a thorny issue, pending more research. |
||
 Among
"clade 12," and closely related to the Sylvia warblers, is the Wrentit
(left) of coastal chaparral and riparian brush from southern Oregon through
the California foothills to northern Baja California. It is currently classified
as a babbler by the A.O.U. (1998), making it the only New World representative
of this family. It is a shy but vocal little bird. Like many Asian babblers,
pairs apparently mate for life and are entirely resident, spending their
entire lives within a few acres of scrub. Like Old World babblers they
are retiring but have characteristic calls. Their "bouncing-ball" territorial
song is easily imitated and is the soundtrack of California chaparral,
but they also give a cat-like purrr and a variety of scolding notes.
At various times the Wrentit has been considered most closely related to bushtits, to titmice, to babblers, to Old World warblers, or to wrens; it has at various times been elevated to its own family [Chamaeidae]. Sibley & Ahlquist (1982) used DNA-DNA hybridization technique to compare it with various babblers and Old World warblers plus a titmouse, a gnatcatcher, a kinglet, and more distantly related birds. The results showed that the Wrentit was closest to the babblers in the genera Trichastoma, Alcippe, and Malacopteron but about equidistant from Old World warblers in the genus Sylvia. Indeed, there are many ecological and morphological similarities between the Wrentit and the Dartford Warbler Sylvia undata of w. Europe and n. Africa. Both inhabit dense thickets of woody shrubs, carry their tails cocked up over the back, have bright irides, eat insects and small fruits, build similar nests, and are highly vocal. Recent genetic work (Burns & Barhoum 2006) shows that the Wrentit
became isolated in the dense California chaparral during the Pleistocene.
Its ancestors presumably arrived in North America across the Bering Straits
land-bridge (although the genetic evidence cannot tell us that). It diverged
from its ancestors between 6.5 and 8.1 million years ago. During the cooler
centuries of the Pleistocene, over 200,000 years ago, its range was probably
restricted to southern California and Baja. With the retreat of the ice
age, its range expanded north through the foothill chaparral on both sides
of California's Central Valley, eventually reaching southern Oregon.
|
||
| Genetic studies of the Wrentit (Cibois 2003, Burns & Barhoum 2006)
have found that its closest relatives are certain Asian babblers in the
genera Alcippe, Chrysomma, and Paradoxornis. However,
the genus Alcippe is non-monophyletic. Some babblers currently assigned
to Alcippe are in Jonsson & Fjeldså's (2006) "clade 12"
[including Golden-breasted Fulvetta A. chrysotis and Streak-throated
Fulvetta A. cinereiceps] but others currently assigned to Alcippe
are in their "clade 13" and not closely related at all [e.g., Rufous-winged
Fulvetta A. castaneceps, Brown-cheeked Fulvetta A. poioicephala,
and Gray-cheeked Fulvetta A. morrisonia]. It is apparent that some
of the Fulvettas will need to be assigned to other genera. What may be
the Wrentit's closest relative is Yellow-eyed Babbler Chrysomma sinense
of southern Asia (Cibois 2003). Presumably Rufous-tailed Babbler C.
poecilotis and the endangered Jerdon's Babbler C. altirostre,
of northeast India, are in this same group.
Also closely related are the parrotbills in the genus Paradoxornis. There are 18 species of these parrotbills, plus Great Parrotbill Conostoma oemodium, which appears to be related. Only four of them have been studied genetically (Cibois 2003) but they closely fit into the set of birds we are discussing on this page. [The other species traditionally placed in the Parrotbill family, 'Panuridae' in the traditional sense, is Bearded Reedling Panurus biamicus, but it is not related to parrotbills at all. It is a very early offshoot of the sylvoid assemblage and is provisionally placed in its own family]. So 19 parrotbills now round out "clade 12," which is provisionally called the Sylviidae here.
|
||
|
The huge bills of Great, Black-breasted, and a few other parrotbills allow them to specialize on bamboo or reeds. Many of the smaller-billed species in Paradoxornis move in mixed species flocks through the forests with babblers, warblers, and other species. Sibley & Monroe (1990), relying heavily on DNA-DNA hybridization evidence, considered parrotbills simply specialized babblers and do not even assign them a "tribe" level within the Timalinae. This is not a new idea; Ali & Ripley (1971) considered them babblers and stuck them in the middle of their babbler list. Both the Birds of the Western Palearctic handbook series (Cramp 1993) and the Birds of Africa series (Fry et al. 2000) lumped parrotbills with babblers but then disagreed about the enigmatic rockfowl of Africa. BWP lumped them with babblers but BoA consider them a separate family [Picathartidae] not closely related at all. The latter position has since been confirmed by direct genetic evidence — rockfowls are not remotely related to this group of birds. However, the entire babbler and allies assemblage needs clarification. While Cibois (2003) and other studies summarized in Alström et al. (2006) and Jonsson & Fjeldså (2006) have made a lot of promise, we do not yet know whether the entire 'babbler' assemblage will be treated as one or two families. For the present, we await further evidence. Two other odd species are found in "clade 12" of Jonsson & Fjeldså (2006). One is Abyssinian (African) Hill-Babbler Pseudoalcippe abyssinica, of east and northeast Africa. Although some assign this bird to the genus Illadopsis, all the other Illadopsis that have been genetically studied prove to be in "clade 13" — closer to the typical babblers and laughing-thrushes (Cibois 2003). The final species is White-browed Chinese Warbler Rhopophilus pekinensis of north China. Although placed among the "Old World Warblers" among all traditional lists, many birders have opined that it acted more like a babbler (including me). The genetic evidence is just in: it is, indeed, closer to babblers and is among our "clade" 12 (Jonsson & Fjeldså 2006). |
||
|
Photos: The Sardinian Warbler Sylvia melanocephala was photographed by Blake Matheson at Monfrague, Spain, on 6 Apr 2005. The Chestnut-vented Warbler S. subcaeruleum was near Brandvlei, South Africa, in July 2006. Bill Hill photographed the Wrentit Chamaea fasciata at Carmel, California, in April 2006. The Black-breasted Parrotbill Paradoxornis flavirostris was photographed in Kaziranga Nat'l Park, Assam, India, on 1 Apr 2001. All photos © 2006 Don Roberson, except the photos attributed to Blake Matheson and Bill Hill, who hold those copyrights, used with permission; all rights reserved. Bibliographic notes There is a "family book" covering the sylvid warblers (or "sylvid babbers," if you will) — Shirihai et al. 2001 — but I have not yet reviewed it in detail. It was meant to, and does, cover the genus but not the lineage that also includes parrotbills, Wrentit, and certain babblers. The next volume of HBW will cover all the sylvoid warblers, but not as a "family" as I have limited it here. Literature cited: Ali, S., and S. D. Ripley. 1971. Handbook of the Birds of India and Pakistan. Vol. 6. Oxford Univ. Press, Bombay & London. |
