On Wednesday I birded as the wind blew and large thunderclouds appeared from the west. I came upon a few dozen swallows perched on a wire. Most were easily identified as Tree Swallows. As you can see in the photo below, Tree Swallows are blueish above and white below, making identification fairly easy. Unlike other swallows, this species can survive on fruit in the winter. Therefore they winter further north than many other swallows and are the first swallows to appear in the spring. Tree Swallows are not universally admired, since they depend on nesting cavities of other birds, like woodpeckers and bluebirds.
A few of the birds gave me pause. They appeared to be smaller than the Tree Swallows and brown-backed. Because their throats were definitely white, my first thought was that these smaller birds were Bank Swallows. (Rough-winged Swallows have dusky throats.) They lacked, however, any semblance of a breast band. If you look closely at the next photo, you may notice a few blueish feathers molting into this juvenile Tree Swallow's back.
The young Tree Swallows had difficulty keeping their balance when they faced the wind. In this last photo the young bird almost toppled off the wire!