It’s a hard time of year to be a birder. Many birds aren’t where they are supposed to be, and many of them don’t look like they are supposed to look. In Roger Tory Peterson’s field guide, first published in 1934, he referred to some of these culprits as “confusing fall warblers.” In truth, many non-warblers are confusing, too.
Several things happen in late summer. It’s migration season, so northern-breeding birds are passing through on their way to the tropics. Some stop in Maine to feed and rest along the way, often in the company of our local birds. Local birds are already moving around more, now that they are not tied to nest sites and demanding kids.
Then there is the color problem. Many birds molt before migrating, sometimes into muted plumages. It helps to be a brightly-colored bird when trying to attract a mate, but being colorful in non-mating season just attracts predators. In some birds, the seasonal change is drastic.
Peterson’s original guide depicted 27 confusing fall warblers, which he described on pages separated from the spring birds. I am hereby throwing all that out. On the spur of the moment, I’m creating my own classification system. There are four categories in my system: feeder birds, birds that don’t change much, birds that change some and birds that change a lot.
Feeder birds are easy. Most are seed eaters. They often don’t migrate far, if at all, and they seldom acquire a less colorful plumage. A few young birds in the backyard might be confusing. Juvenile song sparrows have shiny new feathers, and look brighter than their parents. Young chipping sparrows have streaky breasts, unlike the plain white underbody of their parents, and they lack the reddish cap. Other than that, backyard birds won’t fool you.
Among the non-feeder birds, many don’t change plumage much at all. These include black-and-white warblers, ovenbirds, yellow warblers, Wilson’s warblers, northern waterthrushes, palm warblers, American redstarts and pine warblers. True, youngsters can be a problem. But the little dickens grow up so fast.
Another set of warblers is a little more challenging, partly because males, females and youngsters are foraging together through August. There is enough variation within each family to cause a birder to look twice. The male northern parula looks pretty much the same year-round. Females give the impression of being very yellow underneath. Juveniles are similar, and their fresh feathers look even brighter. Regardless, all the parulas have helpful field marks, especially the conspicuous wing bars.
Black-throated green warblers often inspire a second look. Adult males look pretty much the same all year, but females don’t have much black in the throat even in breeding season, and it fades even more in the fall. Young birds never had the black throat to begin with. So, there are black-throated green warblers all over the woods that don’t have black throats. Fortunately, the rest of the bird looks like the picture in the book, and the strong wing bars help confirm the identification.
Magnolia warblers are challenging. Normally, the heavily streaked breast serves as a good field mark. But it fades in the female’s fall plumage, and the streaks are barely perceptible on the youngsters. But, as usual, the rest of the field marks remain about the same, and the two-tone undertail is a dead giveaway in any plumage.
Nashville and Canada warblers lose a little of their distinctive field marks, but the basic color of the birds remain the same, and the lack of wing bars usually makes them easy enough to identify in fall plumage. That’s the way it goes for most birds. There may be some variation, but it’s not extreme.
But then there are those birds that undergo drastic changes. Male blackburnian warblers are bright orange in summer, but much of that color fades in autumn. Females are bright yellow in spring, but the color almost completely disappears by the time the bird leaves Maine. Juveniles are nondescript. Blackpolls are starkly colored in black-and-white streaks when they arrive in May. When they leave, the birds are a drab greenish-gray color. Worse, they look almost exactly like the bay-breasted warbler, which also loses most of its color. Unfortunately, Cape May warblers do it, too. These birds can be very difficult to tell apart in autumn.
Perhaps the change champion is the chestnut-sided warbler. The bright yellow cap and the chestnut-colored flanks make this bird easy to identify in summer. In autumn, it all goes away.
Bob Duchesne serves as vice president of Maine Audubon’s Penobscot Valley Chapter. He developed the Maine Birding Trail, with information at mainebirdingtrail.com. He can be reached at firstname.lastname@example.org.
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