This month's bird is the Myrtle Warbler (pdf). Peter explains:
The Myrtle Warbler, Dendroica coronata, is the eastern subspecies of the Yellow-rumped Warbler. For years it was considered a separate species, but in 1973 the American Ornithological Society "lumped" it with its western counterpart the Audubon's Warbler and the Guatemalan Goldman's Warbler, to make one species. This bird is the most common warbler in North America, and winters in great numbers along the mid and south Atlantic Coastline due to its ability to eat wax myrtle berries in addition to warblers' usual mainstay diet of insects. During migration it has a soft musical song with a slight trill that fades out. In winter, it has a
very distinctive chip note. Note its yellow side patches and black breast and mask. Its primary diagnostic in all plumages is a yellow patch in its lower back easily seen when in flight. Don't expect to find it nesting in your yard, its heading to forests farther north.
Read the rest (pdf).