 Thrushes
are small to medium-sized songbirds that have ten primaries and a turdine
'thumb' on the syrinx. Many are accomplished songsters, and some have vocalizations
that are among the most lovely on earth. It has been difficult to define
this family as its boundaries are constantly changing in the ornithological
literature. Keith, Urban & Fry's (1992) Birds of Africa said:
"We prefer to retain Turdidae as a family until its relationships with
sister groups are worked out, while recognizing that this is probably in
part an artificial grouping." When I first created this page in 1999, the
Turdidae were a huge family of 365 species. Recently, many authors are
taking the approach used by the 3d ed. Howard & Moore Checklist (Dickinson
2003) in placing the 180 or so "chats" and relatives within the Muscicapidae
[Old World Flycatchers]. I now follow this trend and restrict the Turdidae
to 173 species in 20 to 24 genera of "true thrushes." The family still
retains the familiar genus Turdus — examples of which include the
widespread and familiar American Robin T. migratorius and Eurasian
Blackbird T. merula — and a host of others including bluebirds,
solitaires, whistling-thrushes, alethes, and shortwings.
By far the largest group within our restricted Turdidae are in the 65 species within the genus Turdus. These birds are native to all continents except Australia and Antarctica. Some are common, others are widespread [Island Thrush T. poliocephalus has 51 subspecies scattered widely across the Pacific and on New Guinea and Borneo], but many are scarce and local. One of the latter is Kessler's Thrush (left or above) whose breeding range is restricted to north China. |
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 This
Groundscraper
Thrush (right) is a South African thrush photographed as it battled
its own reflection in a auto windshield. It is most often retained within
a monotypic genus (Psophocichla), of of ten such monotypic families
within the Turdidae. Another is the strange and unique Fruithunter Chlamydochaera
jefferyi, endemic to the mountains of northern Borneo. For many years
it was not known how this pigeon-shaped thrush was related to other birds;
details of its nest and song have only recently been published.
Thrushes and their sister groups have been treated taxonomically in many different ways over the past half-century. They were once considered a part of a huge group including Old World flycatchers, Old World warblers, babblers and allies (Mayr and Amadon 1951). Later the grouping was restricted but still included the batises, monarchs, and whistlers (Wetmore 1960) which are now thought of as separate families. Sibley & Ahlquist (1990) and Sibley & Monroe (1990) created a huge Muscicapidae with two subfamilies -- the 'true thrushes and the rest, which were divided into two tribes, the 'chats' and the Old World flycatchers. Clements (1991) sort-of followed this approach. But if Sibley & Ahlquist's DNA evidence is correct, that grouping ('true thrushes' and 'chats' together but excluding Old World flycatchers) is polyphyletic. There is no genuine consensus as yet, but the restricted arrangement now adopted here seems best. Even this approach is not without problems at the edges: following recent authorities like Keith, Urban & Fry (1992), Urban, Fry & Keith (1997) and (Christy & Clarke 1998), I exclude Chaetops (rock-jumpers) and Horizorhinus (the endemic Dohrn's Thrush-Babbler of Príncipe) from thrushes and consider them (tentatively) to be, respectively, a separate family [Chaetopidae] and a babbler. |
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Setting aside these taxonomic quagmires, let's just review the basics
of the thrush family. A typical example is the American Robin (below
left; at nest with young). These large thrushes sing lovely songs; they
hop on lawns listening for earthworms and pull them from the soft earth;
and their nests can often be easily found. Indeed, they are considered
a harbinger of spring in many places. There are Turdus thrushes
in most wooded habitats around the world. North American woods and riparian
habitats have members of the genus Catharus (e.g., Hermit, Swainson's,
Gray-cheeked & Bicknell's thrushes, Veery) whose spiraling melodies
(some species upscale, others downscale) are among the most beautiful sounds
of summer. One of those species — Hermit Thrush — is shown (below
right). On migration, when they are silent except for flight notes and
calls, members of this group can be very difficult to separate visually,
especially as vagrants. Wood Thrush Hylocichla mustelina of eastern
North America is another fine singer.
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 Included
in the true thrushes re a wide range of species with more limited vocal
repertoires. These are the Zoothera thrushes of the Old World, and
their New World relatives Aztec Thrush Ridgwayia pinicola and
Varied
Thrush (below). These are an ancient lineage of mostly sedentary, secretive,
easily-overlooked forest species (a good summary of the African species,
including identification, is in Clement 1999). The Varied Thrush of western
North America breeds in dark woods of the northwest and is so shy that
it's prolonged note on a minor scale is often the only evidence it is around.
The particular individual shown below was a vagrant in Death Valley. It
is a very odd individual and must have been an immature female (lacking
a breastband) but it also lacked all orange tones on the breast and supercilium.
It is an example of schizochroism: washed-out plumage from a lack of a
pigment. Oddly enough, the only vagrant Varied Thrush to reach the British
Isles was another schizochroistic individual.
In contrast, the North American bluebirds (genus Sialia) are often conspicuous in open country. The lovely sky-blue color of a male Mountain Bluebird (right) especially stands out against the usually pale background that it inhabits: high-elevation plains and meadows in the summer, dry barren grasslands in the winter. I like this shot of a blue bird against a blue sky on a gleaming white old-style grave stone. As it happens, it is only Mountain Bluebird ever to have wintered along the coast of Monterey County, my home county in central California. |
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Tropical forests also have their share of thrushes. In south Asia,
the Greater Sundas, and Taiwan are 7 species of whistling-thrush (genus
Myophonus);
shown (below left) is Blue Whistling-Thrush which frequents the
Himalayas, often found along rushing streams. In Neotropical woods there
are often one or more species of solitaires (Myadestes) — exceptional
songsters that are much easier to hear than to see. The backlit singer
shown (below right) is Rufous-throated Solitaire, a secretive bird
of montane forests in the West Indes.
There were once six species of Myadestes in Hawaii, but four, and probably five, are now extinct. |
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Photos: The Kessler's Thrush Turdus kessleri was singing from a perch on Huzu Pass, high in the mountains of north Qinghai Province, China, on 22 June 2004 [it is a digiscoped photo]. The hyped-up Groundscraper Thrush Psophocichlalitsitsirupa was in Kruger Nat'l Park, South Africa, in July 1996. The American Robin Turdus migratorius was bringing food to its nest in the parking lot of Devils Tower Nat'l Monument, Wyoming, U.S., on 15 June 1998. The migrant Hermit Thrush Catharus guttatus stopped at Big Sur R. mouth, California, on 27 Oct 2001. The schizochroistic Varied Thrush Ixoreus naevia was totally lost at Emigrant Ranger Station (where there is no undergrowth), Death Valley Nat'l Park, California, on 17 Nov 1977. The male Mountain Bluebird Sialia currucoides was photographed at Moss Landing, California, in Jan 2003. The Siberian Blue Whistling-Thrush Myiophonus caeruleus was along a river at Pahalgam, Kashmir, India, on 16 Aug 1978. The Rufous-throated Solitaire Myadestes genibarbis was photographed as it sang on Dominica in March 2000. All photos © 2004 D. Roberson. |
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| Family book: Rating HHHH
Clement, Peter. 2000. Thrushes. Princeton Univ. Press, Princeton, N. J. This is an excellent addition to the family books in the Princeton series. [Full disclosure: I commented on a couple species account during the draft stage.] The plates appear separately near the front: the artwork is rather good in a "field guide" style, although some show welcome background details, opposite summary pages which include small maps. The maps I looked at were quite good. Distinct races are nicely covered. The text cover identification, habitat, breeding biology (very summarized), relationships, and detailed plumage descriptions, plus references which (in contrast to some similar efforts) look reasonably extensive. I don't personally see the need for the detailed plumage descriptions since no book like this can hope to cover the complete range of variation, and they are very tedious to read, but it is the "style" of these family books. There are some helpful extra sketches of plumage details scattered in the text.Other literature cited: Christy, P. and W. Clarke. 1998. Guide des Oiseaux de Såo Tomé et Príncipe. Ecofac, Libreville, Gabon. |
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