A wing bar is a distinct field mark on the top of a bird's wing caused by contrasting colors on the tips of the primary and secondary coverts. Whether the wing is folded at rest or extended in flight, these contrasting tips form a distinct stripe of color across the wing that can be useful for identifying bird species.
About Wing Bars
Wing bars can be prominent, distinctive patches on a bird's wing, making them ideal as a field mark to identify bird species. The bar's unique color is caused by colored tips on the primary and secondary covert feathers of the wing - the feathers that cover the upper bulk of the wing but don't extend into long flight feathers. When those tips are different colors than the bird's overall plumage, a wing bar is visible. Over time, the bars may fade and disappear as the tips of the feathers wear off. In late winter or late summer, depending on the molting cycle of the bird species, the bar could disappear altogether. When the bird molts into fresh plumage, the bar will be back and may look wider, brighter and much more visible than expected.
The overall size, shape, and visibility of wing bars can also change in other ways. The bird's posture may affect how well a wing bar can be seen, and some birds may even hold their wings in ways that obscure the bar altogether. In flight, a wing bar will always be visible. When the wing is spread, the bar will show as a stripe down the center, stretching along the length of the wing roughly from the bird's body to the wingtip, though not all wing bars stretch the entire wingspan.
What Wing Bars Aren't
Birds can have a variety of different markings on their wings, and not all of them are wing bars. Other colorations on a bird's wings that might be confused with wing bars include:
- Wing Stripes: While a wing bar generally crosses the wing when folded and is seen down the center of the wing in flight, a wing stripe is along the edge of the wing. The white-winged dove is an example of a species with a prominent wing stripe. In flight, wing stripes are usually closer to the wing tip and are much broader than a typical bar.
- Wing Patches: Some birds, such as northern mockingbirds and pine siskins, have distinct color patches on the wing. These patches are much more compact than wing bars and show as roughly square, oval or large circular spots on a folded wing. When the wing is spread, wing patches are larger than wing bars but are confined to one area such as on the primary feathers or in one area of the secondary feathers.
- Edging: Many birds have colored edges to their primary feathers that create a delicate striping effect on the wing, but these are not true wing bars. Instead, these fine stripes run along the edge of the primary feathers for the length of the wing, rather than crossing the wing like a bar will. Like wing bars, however, the pale edges may wear off with use and the wing color can appear to change when the bird molts.
Identifying Birds With Wing Bars
Since wing bars are bold and easily seen, they are ideal field marks for birders to use when identifying species. When looking at wing bars to help with bird identification, note:
- Color: Light colored wing bars are more common, but dark bars are also found on some species. Note whether the bar is white, buff or creamy colored or a brighter shade such as yellow or red.
- Number: Birds may have just a single wing bar, but some species have multiple bars. Note how many bars are on one wing, and also note how they compare - one bar is often shorter or thinner than the other.
- Thickness: Wing bars can range from very bold, thick markings to thin, delicate lines. Note the thickness of the bar and if it tapers toward either end. On worn plumage, however, wing bars can look thinner than normal, whereas they may seem thicker on fresh plumage.
- Length: Wing bars do not necessarily extend across the entire wing. Note how long the bar is compared to the overall width of the wing, and compare the lengths of each bar if the wing shows more than one.
- Shape: Most wing bars are relatively straight or show just a short, gentle curve across the bird's wing, but some do have sharper curves or angles. This can be especially visible when the wing is spread in flight.
Wing bars are especially common field marks among sparrows, warblers, finches and other small birds, and understanding how to note the characteristics of the bar can help birders use this field mark easily.