Identifying birds in flight can be a tremendous challenge, but birders who know the parts of a bird's wing can more easily pick out the essential clues that help properly identify the species. Both the structure of the wing and the types of wing feathers can be crucial field marks, and they are easy to learn.
Understanding the basics of bird wing anatomy is a great way to sharpen your bird identification skills. Because wings are so very important to birds, a birder who learns to identify differences in their structure and feathering will be much better prepared to identify species.
Wing Structure of Birds in Flight
When identifying a bird in flight, observing the structure of its wings is the place to start. After noting each of these structural elements, you may have all the clues necessary to make an identification based on information in a good bird field guide. Here are five key structural elements to look for:
The combined length of both wings from wingtip to wingtip can be a vital identification clue. Ideally, judge the wingspan when the bird is holding its wings level so there is no distortion, and consider the complete length across the bird's body. If possible, judge the length by comparison to other birds or nearby objects, which will help you assess more accurately.
Wingtips are easily visible on flying birds, and determining if they are rounded or pointed can help with proper identification. Another clue can be the splay of the primary feathers (how wide the spaces are between each individual feather on the wingtip). Some birds hold these feathers close together, while others spread them widely.
The bend of a bird's wing is its wrist—the first joint down from the wingtip—and how that wrist is held can distinguish different species. As with wingspan, it is best to make this judgment when the bird's wings are fully extended and the bird is gently soaring so that the wing is in a rest position. Check to see if the wrist joint is relatively straight or shows a stronger bend, and how that bend compares to the position of the head. At the same time, check for any markings, such as a dark patch or comma-like shape at the wrist.
The leading edge of the wing is the patagium, and its color can help identify a bird, such as the dark patagium on the red-tailed hawk pictured above. Check to see if the whole patagium is colored or if it is simply splotched or speckled.
A bird's wingpit is the equivalent to the human armpit, the area close to the body on the interior of the underside of the wing. This area can show distinct colors or markings vital for bird identification. Look for streaks, barring, or color patches on any in-flight bird you're trying to identify.
While the structure of the wing is often more immediately useful for field identification, field guides often refer to different types of feathers when listing key field marks. Understanding how those feathers look on a wing can help you be prepared to identify each bird you see.
The primary feathers are the "fingertip" feathers of the wing and are found at the wingtip.
Secondary feathers make up the back edge of the wing closer to the body. They are generally shorter and closer together than primaries, and birds do not manipulate them as much as they do their primary feathers.
Covert feathers make up the wingpit as well as the upper side of the wing, and they cover the base of the primary and secondary feathers. They may be called primary coverts or secondary coverts, depending on which feathers they are aligned with.
Not every bird will show unique identification clues on every part of the wing or every type of wing feathers. Understanding the possible markings, however, will prepare you to identify every mystery bird that flies by.
A perched bird shows a very different, and less helpful, view of its wing than a bird in flight. The same wing feathers can be seen on perched birds, though most of the structural wing parts that are useful for identification are hidden. The patagium, wrist, wingspan, and wingpit cannot be seen properly for identification on perched birds, but the types of wing feathers can still be informational.
The primary feathers make up the longest part of a bird's folded wing and culminate in the wingtip. When the bird is perched, different edging colors are more visible on these feathers, and the primary projection—how far the primary feathers extend beyond the secondary feathers—can be a great clue for identifying tricky bird species.
The secondary feathers are less visible on a folded wing and are closer to the bird's back, though they can overlap significantly and may not be easily seen. As with the primary feathers, look for edge colors that may be visible to provide a clue for identification.
Both the primary and secondary coverts on the upper side of the wing are easily visible on perched birds. These feathers make up the forward part of the folded wing, and their edging or colored tips can create wing bars that are ideal field marks.