BIRD FAMILIES OF THE WORLD
 
 
a web page by Don Roberson
 
 
WRENS Troglodytidae
  • 86 species: 85 (or more) in New World, one in Old World (unless it is split into more)
  • DR personal total: 49 species (58%), 16 photo'd

The wrens are a (almost entirely) New World group of small, active songbirds. Individual wrens can often be hard to see, but they are "always, it seems, dominating the soundscape" (Kroodsma & Brewer 2004). The beautiful cascading song of Canyon Wren (left), for example, brings life to the arid canyon country of the southwestern United States. It is found primarily in steep-walled canyons, and its characteristic and spirit-stirring song echoes between those canyon walls. It is the sound of the Grand Canyon, among other spectacular gorges.

Two close relatives — Sumichrast's Wren Hyorchilus sumichrasti and Nava's Wren H. navai — are very local Mexican endemics. It was the Canyon-Wren-like song that helped us find Sumichrast's among the boulders in coffee-planted hills of Vera Cruz, and it was thrilling when the songster itself finally emerged. It is the song of the wren that lingers.

A good many of the wrens are adapted to desert county, including a good percentage of the striking black-and-white barred wrens in genus Campylorhynchus. An excellent example is Bouchard's Wren (right), almost entirely restricted to the states of Oaxaca and Guerrero. Its habitat is arid thorn-scrub forest with giant cacti. Its Spanish language name implies it eats scorpions, but not enough is known about its lifestyle to say whether this is true.

Its relative, the well-known Cactus Wren Campylorhynchus brunneicapillus of the American Southwest — whose low harsh song is a background standard in Western movies — eats a wide variety of small prey, including wasps, grasshoppers, and small lizards. Plus "some individuals learn to pry squashed insects from car radiator grills" (Kroodsma & Brewer 2005).

Widespread across North America, House Wren (left) is a familiar garden bird. Its bubbly song can dominate a spring walk in riparian habitat in the West, and it builds nests in a wide assortment of spots [unused mailboxes, planter-boxes, or a discarded hat!) in the East. The taxonomy of House Wrens is muddled. Some years ago the AOU lumped "Brown-throated Wren," whose Mexican range reaches s.e. Arizona, with the widespread House Wren, then considered to be a ubiquitous species throughout the New World. Dickinson (2003) listed 32 subspecies for Troglodytes aedon from Canada to the Falkland Islands. Kroodsma & Brewer (2005) started segmenting some of these into species, calling T. aedon "Northern House Wren" but splitting many Neotropical populations as Southern House Wren T. musculus. They even resplit Brown-throated Wren T. brunneicollis, plus split out wrens on Clarion I., Cozumel I., and the Falklands [T. tanneri, beani, and cobbi, respectively]. They did not, however, split very distinctive Caribbean populations, like the ones on Grenada [T. a. grenadensis]; those wrens were very noticeably different to my eye during a one-day stop on Grenada. Dickinson (2004) concedes that splits are due in the Caribbean. There is still a lot to learn about the House Wren.
The other very widespread Troglodytes wren has been called simply "the Wren" in Eurasia — where it is the only member of the family to reach the Old World — and Winter Wren in North America. Recent biochemical analysis suggests that there may be up to six different clades of this wren (summarized in Kroodsma & Brewer 2005), and that western and eastern populations in North America act as to biological species where they meet in the Canadian Rockies (Toews & Irwin 2008). At this writing (March 2010) it is rumored that the AOU will split the American populations this coming July. The "ear-birding" blog has a very good analysis of differences in calls and song between the North American taxa. If this does occur, the one nesting here in California will be called Pacific Wren; this photo (right) is of a just-fledged youngster with gular flanges. It is overall very dark rusty-brown, characteristic of this western group.

Research has shown that the song vocalizations of wrens are learned, at least in common North American species (see Kroodsma & Brewer 2005). One of those impressive singers inhabit marshes: the widespread Marsh Wren (left) that breeds across North America. Males defend territories and build a plethora of dummy 'nests' to attract females. The songs are quite different between western and eastern populations. It is not improbable that they, too, will be split into two or more species.

The only known exception to the rule that songs are learned in wrens involves the North American populations of Sedge Wren Cistothorus platensis. Laboratory experiments that complemented field research showed that each nestling Sedge Wren improvises his own unique song, and no two are exactly alike (more in Kroodsma & Brewer 2005).

Relationships within the Troglodytidae were considered in the biochemical research by Barker (2004), and the relationship of the wrens to other families explored in Barker et al. (2004). Their closest relatives appear to be gnatcatchers. A very odd Amazonian species, Tooth-billed Wren Odontorchilus cinereus, acts much like a gnatcatcher. [Black-capped Donacobius Donacobius atricapilla, which has traditionally been considered an odd wren in Amazonia, is actually an ancient relict of Old World grassbirds, and is best placed in its own family.]

Many wrens are found in the Neotropics. At least 27 are assigned to genus Thryothorus. These are real skulkers in undergrowth thickets, many in humid lowland rainforest, and they are found mostly by their songs. Another group found by song are three species of wood-wrens. White-breasted Wood-Wren Henicorhina leucosticta is a very common lowland species from Mexico to Peru and Brazil. Its highland equivalent is Gray-breasted Wood-Wren (right), which ranges from Mexico to Bolivia (photographed here in Costa Rica).

There are some astonishing wrens that live in the shadows on the floor of tropical lowland rainforest, making them very difficult to observe. But these wrens have fabulous vocal abilities. This quality appears in the names given to some of them, such as Nightingale Wren Microcerculus philomela, Flutist Wren M. usutulas, and Song Wren Cyphorhinus phaeocephalus.

My favorite of these is Musician Wren (below, photo © Arthur Grosset), widespread in the Amazon Basin and scattered among a number of subspecies (this one below is interpositus). Both sexes sing antiphonally, giving a fast, clear, haunting set of whistles, varying greatly in pitch, and switching between different motifs. Anthropologically it sounds like a little miniature boy whistling as he walks through the forest — one can believe it the existence of elves because of this marvelous wren.

Photos: The Canyon Wren Catherpes mexicanus was photographed on 13 Apr 2006 in Anza-Borrego State Park, California. The Bouchard's Wren Camphyorhynchus jocosus at the Tehuacan pueblos, Oaxaca, Mexico, on 20 Dec 1995. The House Wren Troglodytes aedon parkmanii was at Pacific Grove, California, USA, on 1 Feb 2009. The fledgling Western [Winter] Wren Troglodytes pacificus was at Moss Landing, California, on 29 June 2009. The Marsh Wren Cistothorus palustris was on territory in Sierra Valley, Plumas Co., California, on 19 June 1999. The Gray-breasted Wood-Wren Henicorhina leucophrys was at Mirador Cinchona, Costa Rica, on 19 Dec 2007. Arthur Grosset photographed the Musician Wren Cyphorhinus aradus at Rio Cristalino, Brazil, in Dec 2006; see Arthur's many spectacular photos on his website. Photos © Don Roberson, except those attributed © Arthur Grosset, and used with permission; all rights reserved.

Bibliographic note: There is no "family book" per se, but a quite entertaining introduction to this family, with some truly spectacular photos, is in Kroodsma & Brewer (2005).

Literature cited:

Barker, F.K. 2004. Monophyly and relationships of wrens (Aves: Troglodytidae): a congruence analysis of heterogeneous mitochondrial and nuclear DNA sequence data. Mol. Phylog. Evol. 31: 486–504.

Barker, F.K., A. Cibois, P. Schikler, J. Feinstein, and J. Cracraft. 2004. Phylogeny and diversification of the largest avian radiation. Proc. Natl. Acad. Sci. 101: 11040–11045.

Dickinson, E., ed. 2003. The Howard & Moore Complete Checklist of the Birds of the World. 3d ed. Princeton Univ. Press, Princeton, N.J.

Kroodsma, D.E., and D. Brewer. 2005. Family Troglodytidae (Wrens), pp. 356–447 in Handbook of the Birds of the World (del Hoyo, J., A. Elliott & D.A. Christie, eds). Vol. 10. Lynx Edicions, Barcelona, Spain.

Toews, D.P.L., and D.E. Irwin. 2008. Cryptic speciation in a Holarctic passerine revealed by genetic and bioacoustic analyses. Molecular Ecology 17: 2691-2705.

 
 

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