Spring is here and the warblers are back! It’s difficult not to walk with an extra bounce in your step after enjoying a spring morning of watching warblers. Right along with fresh air and budding leaves, warblers embody that sense of rejuvenation we feel as spring replaces a long, dreary winter. The only problem with warblers is that they can sometimes be difficult to see well. As they flit through the trees, often all you see is a splash of color and maybe a quick look at the wing or tail. As we try to piece together such incomplete views, we tend to run through what we did see: yellow breast, greenish back, wing bars… It certainly is helpful to note whether or not a warblers has wing bars. But it would be far more helpful to note what those wing bars actually looked like. After all, not all wing bars are the same, and, in fact, many warblers can be identified on wing pattern alone—even with a quick view. With this in mind, let’s take a closer look at the wing bars of a warbler. Wing bars are formed by contrasting pale tips to the wing coverts (technically, the upper secondary coverts—those feathers covering the base of the secondaries on the upper surface of the wing). The lower bar is formed by pale tips to the greater coverts and the upper bar by pale tips to the median coverts. The lesser coverts are small inconspicuous feathers on the shoulder—they lack pale tips in most species, which is why we don’t see many birds with three wing bars. In the photos below, we’ll look at how variable wing bars can be. Keep this variation in mind while you’re out in the field, and try to get in the habit of observing the different patterns that wing bars make. It may be that a brief glimpse of the wing is all you need to reach a correct identification.
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Figure 1 – Nonbreeding male Yellow-rumped Warbler, October. Yellow-rumped is our most abundant spring migrant warbler, and one of the first to pass through, so it provides a good standard for reference. A Yellow-rump’s wing bars are bold but relatively thin. They are also quite long, being comprised of almost every wing covert feather except the upper few greater coverts. The bird shown is a nonbreeding male. In spring, male Yellow-rumps show more extensive white on the greater coverts but females show a pattern much like the bird in the photo. |
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Figure 2 – Male Black-throated Green Warbler, May. Compared to Yellow-rumped Warbler, these wing bars are much thicker—notice that the dark area between the wing bars is no thicker than the wing bars themselves. Female Black-throated Green’s wing bars are a bit thinner but still much thicker than a Yellow-rump’s. |
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Figure 3 – Breeding male Black-and-white Warbler, May. Black-and-whites show very bold wing bars with every covert feather being black with a white tip. But unique to Black-and-white is the bold white “handle” off the greater-covert bar created by thick white tertial edges. Many other warblers have pale or white tertial edges but only on Black-and-white are those edges so thick as to make a bar equally bold to the wing bars. |
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Figure 4 – Female Northern Parula, September. Northern Parula’s wing bars are thick and bold but they are also uniquely short. Notice that only about half of the wing covert feathers are tipped with white. The others are solid blue-gray, blending in with the extensively blue-gray upperparts. The effect is that a Northern Parula has wing spots more than wing bars. Those venturing south should note that Tropical Parula has a similar wing pattern. |
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Figure 5 – Breeding male Blackburnian Warbler, May. At the other extreme from Northern Parula, a male Blackburnian Warbler in breeding plumage has the upper wing coverts mostly white, creating a big white wing patch with two spurs of white extending below. Breeding plumage Magnolia Warbler has a similar pattern. Note, however, that female and nonbreeding Blackburnians show much less white. |
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Figure 6 – Nonbreeding male Cape May Warbler, October. Cape May Warblers have a unique wing pattern that enable identification of both bright and dull birds. Breeding adult males show the most white and immature females the least, but the pattern is still about the same (the bird pictured shows an intermediate amount of white). The key to notice is that only the median coverts show a white bar. The greater coverts show distinct pale edges but these feathers are not any paler at their tips so there is no second wing bar. |
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Figure 7 – Adult male Prairie Warbler, May. Prairie Warblers show broad, ill-defined yellowish wing bars. The pattern may be weak but there’s no mistaking this wing for one with crisp white wing bars or one with no wing bars at all. |
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