Laura Erickson's For the Birds

Two weekends ago I led a field trip to Park Point in Duluth for the Nature Conservancy. Migration was over, and Park Point is pretty disturbed habitat for woodland birds, so there wasn’t a whole lot to see, but one of the sounds that continued throughout the four-hour visit was a desperately lonely male Pine Warbler. Pine Warblers belong in large stands of mature pine, not in the one little row of pines at Park Point, but he seemed optimistic enough that just maybe, if he sang loud enough for long enough, a female would join him.

I see lots of Pine Warblers every summer when I teach an elderhostel class on the north arm of Burntside Lake near Ely. There’s lots of mature white pine up there, and I get to listen to Pine Warblers to my heart’s content. Bird books often claim that Pine Warblers are tame and trusting, and thus pretty easy to see, but although that may well be true, in my experience those huge pines are mighty effective at covering up any Pine Warblers that may be lurking within.

Since their song is so much like a Chipping Sparrow’s, I bet lots of Pine Warblers go unidentified by people nearby. Both Chipping Sparrows and Pine Warblers sing a simple trill, but the chippie song is dry and mechanical. The Pine Warbler’s song is a bit more fluid and musical.

Pine Warblers return to the Northland earlier than Chippies–often in April when snow still covers the ground. Although they come just about as early as the first Yellow-rumps, they aren’t as noisy and noticeable, and most birders pretty much miss them. Up here they pretty much stick to pine trees, but on migration they can be found in just about any kind of tree. They winter as far north as southern Illinois, and so their migration is pretty short and they are often feeding babies up here before more tropical warblers even return. In winter they flock with bluebirds and Chipping Sparrows, as if they were a sociable kind of bird, though they’re rather scrappy with members of the flock and get into lots of fights. Their winter diet includes lots of berries and pine seeds, and their intestines are longer than the intestines of most other warblers to help them digest this plant material.

In summer, in order to raise four or five growing babies who need plenty of protein, they spend most of their time catching insects, and pretty much seem to ignore the birds around them, sticking to the business at beak. They voraciously gobble up all kinds of insects, from delicate moths and mayflies to hard-bodied beetles, making us think about Calvin and Hobbes’s question–do Pine Warbler burps taste like bugs?