Laura Erickson's For the Birds

Every spring, birders anticipate the arrival of northward-bound warblers with enthusiasm and excitement. Male warblers, their plumage at its most vivid, call our attention to themselves with frequent singing, so the warblers we notice are usually the easiest to identify.

But every fall, birder anticipation of southward-bound warblers is tinged with fear and dread. Although most adult males look just as lovely as they did in spring, they stopped singing weeks ago, making them far less conspicuous than they were in spring. Females are always trickier to identify than males, and adults of both sexes are outnumbered by the babies they produced this year. These immature warblers are notoriously difficult to identify, referred to in field guides as “confusing fall warblers.” In any flock of fall warblers, we’re likely to encounter vireos, flycatchers, and kinglets, all nondescript little birds that add even more complications to fall warbler identification. And to compound the difficulties, all these birds are highly animated. Sometimes we lose sight of one in foliage, and a moment later a similar but entirely different bird is in the same spot.

How do experienced birders distinguish all these hyperactive little dickybirds? And, perhaps more important, why bother?

The first question is longer, but easier, to answer. The most important thing experienced birders have in their bag of tricks is a sense of the possibilities. Take a few moments each day to thumb through the warbler pages in a good field guide. Based on the range maps, notice which ones are most likely to migrate through your area. Habitat, a critical aid to warbler identification in summer, is worthless once the birds start migrating. The most urban backyard can attract a dozen species during migration, when birds are passing through unfamiliar areas.

When you spot a warbler, first consider the easy possibilities. The only ones with bright orange are adult male redstart and Blackburnian Warbler. An orangey tinge on the flanks indicates a chestnut-sided or bay-breasted male. Conspicuous yellow squares on the outer tail make it a female redstart. Conspicuous white squares on the tail are found only on magnolia warblers. Both these species often flare the tail, making these marks more noticeable.

In autumn, if the bird is marked with nothing but clean black and white, it’s a black-and­ white warbler.

The most common two species are the yellow-rumped warbler, which has a bright yellow rump (above the tail), and the palm warbler, which has a distinctive yellow crissum–the marking beneath the tail. Both species make distinctive tsk notes-I somehow hear the yellow-rump’s as an annoyed math teacher and the palm warbler’s as an annoyed music teacher, but tricks for remembering bird sounds are highly individual.

A few warblers are more subtle, but still fairly easy if you notice details. Black-throated green females and young lack the black throat of their name, but have bright yellow faces and dark gray wings with white wingbars. Female and young chestnut-sided warblers don’t have chestnut sides, but do have a distinctive green-yellow upperside and clean­ looking white underside. This species dramatically changes from spring to fall, but its clean appearance, white eye ring, and tropical yellow-green back make it distinctive.

If the warbler is none of the easy ones, you have to practice seeing as many field marks as you can while the bird is in view. Try to take special note of wingbars, the color of the rump and crissum, and any facial markings, especially eye rings and eye lines. At first, many or even most of the warblers you see may go unidentified. But with practice and a good field guide, you’ll figure out more and more.

But why bother in the first place? Identifying warblers is a delightful game. These tiny birds that fly on their own power all the way down to the tropics each fall, and return to north country every spring, piloted by instinct, navigating by the stars, and fueled by insects, are each a tiny miracle of feathers and spirit. And any time we open our eyes to a genuine miracle, our universe expands and becomes richer.