Thursday, May 2, 2013

Midwestern Mimics

In spring, when birdsong is most intense, even non-birders take note of the varied tunes offered by our mimic thrushes.  Composed of short, repeated phrases that mimic the calls or songs of other birds (or even the mechanical noises that arise from human habitation), the intense songs of these residents are hard to ignore.  All three Midwestern mimic thrushes usually forage on or close to the ground, where they consume a mixed diet of insects, nuts and berries.

Best known of this group is the northern mockingbird, a resident of suburbs, farmlands and wood margins.  Easily identified by his black and gray plumage and his prominent white wing patches and white outer tail feathers that appear in flight, this common and aggressive bird delivers each phrase several times and may sing day or night.  Our second mimic is the brown thrasher, sporting cinnamon plumage on his upper side and black streaks on his white chest and abdomen; the male prefers to sing from an exposed perch (often atop a tree) and generally repeats each phrase 2-3 times.  The third and least conspicuous of our Midwest mimic thrushes is the gray catbird, which usually skulks about in low shrubs and forest understory; dark gray in color with a black cap and tail (and a rusty patch on the underside of the tail base), its song is less strident than that of the mockingbird and thrasher and is interspersed with episodes of cat-like mewing.

Though not a mimic thrush, the yellow-breasted chat, a large warbler, is also known for his repetitious song, composed of various squeaks, trills, clucks and whistles.  This extrovert is inclined to sing from the top of a shrub or hedgerow and is easily identified by his white spectacles, his thick black bill and his bright yellow chest.