After leading field trips for many years, I’ve noticed a common pattern among birders. When a small bird is under study, if it takes flight, most of the binoculars go down. This is certainly understandable. After all, it’s not that easy to follow a bird in flight, particularly a small bird that has just taken off from right next to you. Also, in many cases, a decent view of the bird was already had by the time it flew, so why keep looking?
Of course, most of us are accustomed to looking at some types of birds in flight. Raptors and seabirds come to mind right away–most of these birds are large and occur in open areas where they are relatively easy to track in flight. In many cases, these species are seen in flight more frequently than they are perched or resting on the water. As a result, we probably have an easier time identifying some of these species on the wing than at rest because we are so accustomed to looking for their telltale flight characteristics. Other groups like swallows are a bit more challenging to view in flight, being smaller and more prone to quick changes in direction, but we see them in flight often enough that we are accustomed to IDing them on the wing. But most small birds, such as flycatchers, wrens, warblers, and sparrows, are much more challenging to view in flight.
So why bother studying smaller birds in flight? The obvious answer is “why not?” Of course, there are other reasons as well. Whatever reason you have for going birding, the results of your outing will probably be more satisfying if you identify a higher percentage of the birds you see, which will always include birds in flight. If you are doing a breeding bird survey, for example, you will get much better results if you can identify birds in flight. The same is true if you are doing a Big Day or a Christmas Bird Count. If you are out walking the dog or driving to the grocery store, the practice of identifying birds in flight will increase the percentage of birds you identify “naked eye” when binoculars are not handy. And, if you bird at a migration hotspot like Cape May, hopefully there will be days when you encounter large numbers of flying birds. Why not try to get the most out of such spectacular migration events by paying closer attention to birds in flight?
So how do you go about learning to identify birds in flight? The next time you are looking at a Blue Grosbeak or Song Sparrow perched right in front of you, just keep watching when it flies. The first hurdle will be keeping your binocular on the bird and that just takes practice (remember, it’s your eyes following the bird; your binocular is just in front of your eyes). The more accustomed you get to following a bird in flight, the more detail you will begin to see on those flying birds. And, with further practice, the distance at which you can identify flying birds will increase (and identifying closer birds “naked eye” will become routine). Which details to look for on a flying bird will vary somewhat between different families of birds, but your observations should always boil down to the same basic principles of identification (listed below) that apply to birds in any situation:
1) Size – Size is often easier to judge on a flying bird than on a sitting bird. This is largely because flight style is directly related to size. For example, a Broad-winged Hawk soars in tighter circles and flaps more quickly than the larger Red-tailed Hawk. Likewise, the bulky Northern Waterthrush looks much steadier in flight than the comparatively petite Northern Parula.
2) Structure – Structure is always a critical field mark, but what you see and what you should focus on will depend on how good a view you get. On a very close bird, you may see many details of structure such as bill shape, leg length, relative lengths of primaries, etc. On more distant birds or in briefer views, however, you may get only a general impression of structure. Both are valuable. When evaluating general body shape, it is often particularly helpful to think about distribution of weight. For example, a Caspian Tern with its big bill, big head, and thick chest tends to look front-heavy. The much slimmer Royal Tern looks comparatively skinny in front and heaviest in the belly. Wing shape may also be a critical difference between similar species, such as the pointed wings of a Brown-headed Cowbird compared to the rounder wings of a Red-winged Blackbird. In general, wing shape is easier to see on larger birds (such as hawks), which tend to flap more slowly, than it is on smaller birds (like warblers), but it is always important to notice.
3) Behavior – The behaviors to consider with a bird in flight include habitat selection, foraging style (if the bird is foraging), flocking behavior, and, of course, flight style. When looking at flight style, it is often helpful to break it down into several parameters. First is flight path. Is the bird flying directly in a straight line? Is it undulating? Is it steady, drifting, swirling, erratic? Next is wing motion. Is it flapping sometimes, all the time, or not at all? What does it do with the wings when it’s not flapping – open-winged glides (like most raptors), closed-winged glides (like most warblers), something in between (like American Robin)? How fast are the wingbeats? How deep are the wingbeats and is the depth equal above and below the body or different? How much do the wings flex during a flap? This may seem like a lot of characters to consider but in different situations, each may be important for distinguishing similar species. Flight speed is sometimes worth noting. For example, an American Kestrel simply lacks the “overdrive mode” of a Merlin, though Merlins will fly more slowly at times. It is important to realize that flight styles may vary considerably under different conditions or under different behavioral circumstances. Only field experience will teach you the degree to which each species may vary in flight style.
4) Color Pattern – Using color patterns to help identify birds in flight is exactly the same as using these characters on resting birds: sometimes they are very distinctive and sometimes they help only if you know something about what plumage the bird is in. There’s no big secret. However, it should be noted that studying resting birds at a distance (or closer birds “naked eye”) will help you to notice many general color patterns that may not be as obvious when looking at a bird up close. This is an underappreciated fact about field identification: there are often different field marks to use for close birds versus distant birds, and, in fact, some of those “distant” field marks may be much less noticeable on a closer bird. For example, a Least Sandpiper in any plumage looks dark-headed at a distance, with white restricted to the belly. Up close, that field mark breaks down as white markings in the throat and face become apparent. Of course, lighting conditions will also affect what a bird looks like. For example, a pale yellow wash on the breast of a Northern Waterthrush may look bright yellow under early morning light. But then, under the same light, a Yellow Warbler will look really bright yellow. Learning to calibrate your color perception under different lighting conditions is an important part of all types of birding.
5) Voice – Even before you see a bird in flight you may already have identified it by its call. Voice is that extra dimension in bird identification that can function independent of visual characteristics. However, don’t ignore calls that you can’t identify to species. In many cases, a combination of voice and visual characteristics may be needed to reach an accurate identification. For example, Tennessee, Nashville, Orange-crowned, and Black-throated Green Warblers all share a very similar short rising “seep” flight call. Call alone may not necessarily identify it, but if you hear one of these birds and see that it has a bright yellow belly, you’ll know it is a Nashville.
The series of photos below present examples from several different families of birds, with captions highlighting the types of field marks that are most useful to identify them in flight.
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Figure 1) American Kestrel, September, New Jersey. Most birders are accustomed to looking at raptors in flight. Their large size and tendency to occur in open areas make them relatively easy to track in flight. As a result, much has been written about their in-flight identification. A good strategy for learning to identify small birds in flight is to take what we know about raptor flight ID and apply it to smaller birds. In a close view like this, plumage characters are distinctive. At a greater distance, however, shape and flight style become more critical. Like other falcons, American Kestrels show long tails and long pointed wings, but the proportions are different: note how the thickness of this bird’s body extends beyond the trailing edge of the wings, unlike Merlin. American Kestrels have a floating flight, like a paper airplane. Merlin’s flight is much more steady and direct. American Kestrel’s wing strokes have a snap to the downstroke compared to Merlin’s more even-paced wing strokes. |
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Figure 2) Hairy Woodpecker, June, North Dakota. Most woodpeckers have a distinctive manner of flight, alternating a series of quick flaps with a “closed-winged glide”. Because these birds are so heavy, the result is a deeply undulating flight path, falling when the wings are closed and rising again when flapping. But not all woodpeckers fly this way. Red-headed Woodpecker exhibits much slower flaps interspersed with a combination of open-winged and close-winged glides. The resulting wing strokes look more crow-like and the flight path more level. To distinguish this bird from Downy Woodpecker, note the relatively large head and bill and clean white outer tail feathers. In the field, this bird’s larger size would probably be apparent. |
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Figure 3) American Robin, November, New Jersey. American Robins often fly in loose flocks on one level. Several large flocks may take on the appearance of layers of birds in the sky. Their flight is direct and level with no undulation. Their wingbeats are flickering, with quick changes between wide open and half closed where they set their wings for brief glides. |
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Figure 4) Cedar Waxwing, September, New Jersey. Cedar Waxwings often form dense flocks which take the form of a ball. Each bird has a clean-cut shape with pointed wings, pointed face, and clean-cut tail tip. The flight is fast and somewhat swirling, alternating quick flaps with brief closed-winged and open-winged glides. Bobolinks may appear similar in flight, though they tend to form sparser flocks which tend to be aligned in elongated wingtip-to-wingtip ovals. Bobolinks look a bit more elongated, both through the body and wings, and show a double-pointed or spiky tail tip. |
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Figure 5) American Redstart, September, New Jersey. Even when backlit, an American Redstart’s shape is distinctive: long club-shaped tail, longish body, and relatively short, rounded wings. With a little favorable light, the broad black tail tip is usually evident. The flight path is tacking with frequent direction changes. Wing strokes are “soft” (with much flex to the wings), interspersed with closed-winged glides. |
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Figure 6) Blackpoll Warbler, September, New Jersey. Having one of the longest migrations of any songbird, it should come as no surprise that a Blackpoll Warbler is a strong flier. Compared to other warblers, they have relatively long, pointed wings and their wing strokes are very stiff with little flex to the wing. They mix bursts of strong flaps with closed-winged glides, their bullet-shaped bodies cutting through the air more quickly and more directly than do most other warblers. |
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