Swainsons Thrush, Singing, Kaskey Park, University of Pennsylvania, Philadelphia

May 20th, 2013, by Alex Zorach

This photo shows a Swainson's thrush, singing in an American holly tree. I photographed this bird in Kaskey Park, a small park in the middle of the campus of the University of Pennsylvania in Philadelphia.

ID Tips:

The Swainson's thrush is one of the trickier thrushes to identify visually. I find it easier to tell apart from the Wood Thrush, which is larger and has a reddish head, and very big, bold black spots on its breast, and from the Veery, which has only very faint spotting on its upper breast, and a mostly bear white breast. The intermediate spotting on this bird is characteristic of Swainson's thrush, but the spotting pattern is also similar to Hermit Thrush and Gray Cheeked thrush. Hermit Thrush is easily excluded with a clear view of the back and tail--these birds have a reddish tail and rump, contrasting with a more grayish-brown back and head. On the Swainson's, this is more uniform.

The buffy eye ring and buffy face are often-cited field marks for this bird. I personally have found this mark to be an unreliable characteristic: it does little to distinguish the bird from a Hermit Thrush, in particular, although it is more reliable for telling it from Gray Cheeked thrush. This photo shows a very clear view of the eye ring, and the buffy coloration on the face. Not all birds look as clear as this one.

Behavior is also an important cue, easily as important in identification as plumage. Swainson's thrushes are the only thrush to commonly forage in trees, gleaning food from the foliage. Other thrushes feed mostly on the ground, and only fly up into the trees when threatened. A thrush actively foraging in the treetops is probably a Swainson's thrush.

Song:

I find the Swainson's thrush easier to identify by song than by appearance. Its song is similar to that of a Veery, with a series of repeated rolling phrases, with an ethereal, flutelike quality. It starts at a similar pitch to the Veery, but instead of descending to a very low pitch, it ascends to a very high pitch, typically sounding thin at the top. I like to say that a Veery's song sounds like you flushed a Swainson's thrush down the toilet and the song is reverberating through the plumbing on the way down.

Here is a video showing this species' song; the video is not mine:

Migration timing

Yet another clue is migration timing and range limits. In Philadelphia county, where this bird was observed, the Hermit thrush is an uncommon winter resident. One actually began wintering in Kaskey park, but left before staying the whole winter. For hermit thrush, migration peaks through April, where the bird is common, and stragglers occur through May when the bird becomes uncommon. Swainson's thrush is never recorded before April, and is rare as a migrant during April. It only becomes common (but not as abundant as the Hermit thrush) during the second and third weeks of May; it is entirely absent by June.