Friday, February 26, 2010
The towhee is a member of the sparrow family, though it is larger than most sparrows. In size and shape it resembles a cardinal, with a long tail but without the crest. The plumage is jet black on the top side, wrapping around the head to create the look of an executioner’s hood. The belly is white and the flanks are a rich robin-like reddish-brown. The white tips of the outer tail feathers flash brightly in flight. The female is similar except that the black is replaced by brown.
This bird spends a lot of its time on the ground, oftentimes giving away its presence by rustling loudly among dead leaves, stirring them up with a two-footed jump-scratch motion to find insects and seeds – a technique also favored by White-throated Sparrows. In winter it also feeds on acorns and berries.
They have declined greatly in the northeast, perhaps by as much as 90% over recent decades. Two major factors seem to be responsible: habitat loss as its preferred shrubby second-growth thicket areas are reclaimed by mature woodlands; and nest parasitism by brown-headed cowbirds, to which it seems particularly susceptible.
What’s in a name?
If you have a field guide published before 1995, you won’t find Eastern Towhee in it, because there was no such thing. The bird existed of course, just not the name. Those older field guides will include Rufous-sided Towhee, a nicely descriptive name, and that is the same bird we are talking about here. More on that later.
The scientific name is Pipilo erythophthalmus, Pipilo meaning “to twitter or chirp” and erythophthalmus meaning “red-eye.” Most towhees do indeed have a red eye, although many in the southeast have a white eye. The common name of towhee is onomatopoeic, intended to reflect the sound of the bird’s call. An old alternative name, chewink, is derived from the perceived sound of the same call. The second note rises in pitch. The song is very distinctive, though generally not heard in the winter. It is often represented as “drink your teeeeaa” – the last syllable a long, drawn out high-pitched trill. Recordings of the call and song can be found online at http://www.allaboutbirds.org/guide/Eastern_Towhee/sounds.
Stay or go?
I noticed a male towhee in my yard on Thanksgiving Day, and have seen him regularly since then, usually with a group of White-throated Sparrows. Interestingly enough, about half a mile away on Acton Street, Marty Schafer has had an overwintering female towhee. Although they twitter, they apparently don’t Tweet as the two do not seem to have made contact.
Towhees breed throughout Massachusetts, but generally spend the winter months in the southeastern US. From time to time some individuals stay around for the winter. In the Carlisle section of the Christmas Bird Count, towhee has only been recorded on four occasions since 1973, but three of those have been in the last seven years. Marty’s female obliged for the count this year, while mine stayed hidden. Looking back at 100 years of records for Christmas Bird Counts throughout Massachusetts, a similar pattern emerges but with a fascinating twist: significant numbers were recorded between 1950 and 1960, and again in the decade since 2000, but virtually none in the years between, or before 1950.
In contrast to last year, when several more northerly species were observed in this area, it seems that this winter there have been more normally migratory birds staying around. Northern Flicker and Red-winged Blackbird are some other birds I have observed overwintering locally this year that normally do not. Why would a normally migratory bird stay here for the winter? It has nothing to do with the mildness or severity of the weather; after all they cannot know that in advance. Flying south is hard work, and if there is adequate food available (such as a good acorn or pine cone crop), any bird that manages to survive the harsh winter conditions is in prime position to claim the most attractive breeding territory before the migrating birds return. The downside of course is having to endure the cold weather, and difficulties of finding food when snow and ice cover the ground.
Splitting and lumping
What happened in 1995 was that the American Ornithologists’ Union, the authority that decides such things, “split” the Rufous-sided Towhee into two separate species: Eastern Towhee and Spotted Towhee (which is found in the western U.S.). It all comes down to the definition of a species, which itself seems to evolve much faster than the species it strives to define. A common definition is “a group of organisms capable of interbreeding and producing fertile offspring of both genders, and separated from other such groups with which interbreeding does not (normally) happen.” Recent scientific research has focused more on DNA analysis. Long ago, the eastern and western forms of towhee were considered different species: my 1939 “Book of Birds” lists Red-eyed Towhee (Eastern) and Spurred Towhee (Western) as different species. They were subsequently “lumped” together as different “races” of the same species (Rufous-sided Towhee), then “split” again in 1995 to Eastern and Spotted. The two have different calls, and their breeding ranges have only a very slight overlap in the Great Plains, but interbreeding sometimes does occur when they come into contact. This is a phenomenon exhibited by many American birds, having analogous forms in the Eastern and Western halves of the country, some of them considered different species, some of them not (or not yet). The evolutionary divide is believed to have come from the ice sheets that separated the two halves of the continent in the Great Ice Age.
References: Massachusetts Breeding Bird Atlas, edited by Wayne R. Peterson and W. Roger Meservey. The Sibley Guide to Birds, David Allen Sibley. Cornell web site (www.allaboutbirds.org) ∆
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