How to Identify Birds in Flight

How to Identify Birds in Flight
Copyright 2015 by Greg Gillson. All rights reserved.
December 6, 2015







“For the most part when we see a flying bird,
  we watch it with the vain hope that it will land.”
– Christopher L. Wood –






Introduction

Birds fly. At least, most can. In fact, “flight is the defining characteristic of birds” (as  Jonathan Alderfer and Jon Dunn and Kenn Kaufman write). Then why don't field guides teach us to identify birds in flight?

Depending upon the type of birding you are doing, your first detection of a bird may be of a bird in flight. For instance, you are walking along a hedgerow and previously unseen sparrows fly up from the grass and disappear into the brambles. You turn a corner and a bird takes off from a tree and flies away. Movement catches your eye and you see a flock of birds flying in formation overhead. You scope out the ocean from a promontory and view numerous birds winging by offshore.

These are the common ways that we see birds. It only makes sense that your field guide should tell you how to identify these birds in flight. But they don’t. Oh, some occasionally mention the unique flight styles of a certain few birds. There are a few specialized guides for hawks and ducks in flight. But these books are often based only on shape and pattern, not actually the behavior of flight that might help you to identify distant or quickly-viewed birds.

This manual teaches you the basic mechanics of flight and gives you the vocabulary necessary to describe a bird in flight in such a way that you may identify it to family or even species by flight alone. Combine flight style with flight call notes or key observable plumage field marks, and most birds in flight are readily identifiable.




Part 1: Flight style mechanics

Purpose or style of flight

As a horse may walk, trot, canter, or gallop, not all bird flight is the same, either. To start with, if possible, concentrate on commuting or soaring flight, as described below, as these are the “typical” flight styles used when identifying birds. Also take note of any flocking behavior.

Commuting flight, or cruising flight, is prolonged, flapping flight taking a bird from one place to another. This style of flight is the “natural” flight style of most birds. This is the flight style on which to concentrate to best identify birds in flight.

Soaring flight is prolonged, non-flapping flight with wings extended. Birds soar in level flight, circle to gain altitude, or have an S-shaped rising and falling progression for certain long-winged seabirds. For certain long-winged raptors or seabirds this is the “natural” or predominant flight style.

Gliding is shorter-duration flight with wings extended or only partially open. It may be brief glides between bursts of flapping flight, or it may be longer glides on set wings as a bird descends from high in the air to the ground. In general, gliding loses altitude.

Hovering flight is performed habitually by several species to remain in relatively the same position while hunting or over a spot above land or water. Certain birds hover-glean to feed at the tips of tree branches.

Landing and taking off is done by all flying birds. Certain water birds may run on the water to become airborne, while others leap directly into flight. Some flycatchers may pump their tails once or twice upon landing. For most land birds, however, this part of flight is not distinctive.

Chasing and fleeing flight is usually characterized by continuous, rapid, deep wing strokes and twisting or darting flight and is not usually useful for identification.

Feeding flight is performed by aerial feeders such as swallows and flycatchers, and sometimes by other groups of birds, as well. Birds often circle around or fly out-and-back from a perch (flycatching).

Courtship flight may be highly stylized and choreographed, may include other birds, and might be extremely different from the normal flight (oystchercatchers, hummingbirds, larks, American Goldfinch)

Flocking flight may be two birds or two thousand. How do they fly individually and as a group when they are together? Is the flock organized or chaotic? Is the flock compact or loosely spread out?




Silhouette and shape

When observing a bird in flight note first its shape: its outline or silhouette. Notice the shape of the wings and tail, and note shape of the bill, length of the neck, and if the feet trail behind the tail.

A little anatomy: the wing

The wing of birds is analogous to the arm of humans. This is most evident in very long-winged birds such as an albatross, but it applies to all birds (ask for a wing at your next chicken dinner). Keeping it simple without being too inaccurate, they have a shoulder, upper arm (brachium) with the humerus bone, elbow, lower arm (forearm) with the radius and ulna bones, wrist or bend of the wing, and hand (manus).

Primaries are attached to the hand. They are numbered from inner to outer. The innermost primary on an albatross, for instance is P1, the outermost is P10 (Figure 1). Most bird species have 9 or 10 primaries, but the range is 8-12, and 16 for ostriches.

Secondaries are attached to the ulna on the forearm. Birds have a variable number of secondaries depending upon the length of the wing. Some hummingbirds have as few as 6 secondaries; some albatrosses have as many as 40 secondaries.

True tertials, or tertiaries, are feathers attached to the humerus. They are not considered flight feathers. Very long-winged birds have more tertials than short-winged birds. Some bird families, including shorebirds and gulls, have modified tertials that are longer and distinctively marked. In many smaller birds the humerus is so short as to be lacking separate tertial feathers. However, sometimes the inner three secondaries on passerines are called tertials when differently shaped or colored than the other secondary feathers.

Primaries and secondaries are called the flight feathers of the wing or remiges. The tail, with its retrices are also considered flight feathers.

How to Identify Birds in Flight
Figure 1: Black-footed Albatrosses have 10 primaries, 25-29 secondaries, and numerous tertials.

Figure 2: Most gulls, like this Western Gull, have 10 primaries, 24 secondaries, and a few true tertials.
Figure 2: Most gulls, like this Western Gull, have 10 primaries, 24 secondaries, and a few true tertials.

Figure 3: Vaux's Swifts have 10 primaries, but only 6 (or 8, if you count very tiny) secondaries.
Figure 3: Vaux's Swifts have 10 primaries, but only 6 (or 8, if you count very tiny) secondaries.


Shape of the wing

Now that you have learned the all important meanings of the terms arm, hand, primaries, and secondaries you are ready for the next step: describing the shape of the wing. The many different shapes of bird's wings are formed by combinations of arm length and the length of primaries and secondaries.

Narrow wings are formed when the secondaries are all short (Figure 1).

Broad wings are formed when the secondaries are all rather long (Figure 4).

Pointed wing tips are formed when the outer primary is longest and each succeeding primary is a bit shorter, until the innermost primary is about the length of the secondaries, which are all about the same shortness (Figure 1 and 3).

Rounded wing tips are formed when the the outer primaries are shorter and the other primaries are all more-or-less the same length (Figure 4).

The gull's wing (Figure 2), while having a pointed tip, is not quite as narrow-looking as the wing on the albatross and swift. The step from primary to primary is not as great, and the outer secondaries are not as short as the inner secondaries.

Compare the distance from the shoulder to the wrist (arm) and the wrist to the wing tip (hand). The albatross has a long arm (Figure 1). The distance from shoulder to wrist is much greater than the distance from the wrist to the wing tip. The arm and the hand on the gull are about equal (Figure 2). The long hand on the swift is much longer than the short arm (Figure 3).

The individual wings can be relatively flat (Figure 6) or strongly arched (Figure 5).

The shape of the leading edge of the wing is defined by the wing bones and angle of the elbow and wrist. The typical posture may be held rather straight (Figure 6) or forward at the wrist (Figure 7). Likewise, the trailing edge of the wing has a shape defined both by the length of the arm bones and their posture, as the leading edge of the wing, but also by the length of the secondary and primary feathers.

The outer primaries of certain raptors may have notched feather ends. This creates the impression that each primary feather is an individual “finger” rather than one solid wing. Compare the outer 3 primaries on the vulture (Figure 6) with those of the pelican (Figure 4), both of which have broad, rounded wings.

Figure 4: Brown Pelicans have very broad, rounded wings.
Figure 4: Brown Pelicans have very broad, rounded wings.

Figure 5: The pointed wings of Northern Fulmars are gently arched.
Figure 5: The pointed wings of Northern Fulmars are gently arched.

Figure 6: The flat wings of a Turkey Vulture are held in a dihedral (shallow 'V'). The leading edge is rather straight. Notched primaries create a “fingered” appearance.
Figure 6: The flat wings of a Turkey Vulture are held in a dihedral (shallow 'V'). The leading edge is rather straight. Notched primaries create a “fingered” appearance.

Figure 7: Ospreys characteristically arch their wings, holding their wrists forward and up, then hold their hand back and down, The long wings taper to rounded wingtips.
Figure 7: Ospreys characteristically arch their wings, holding their wrists forward and up, then hold their hand back and down, The long wings taper to rounded wingtips.

Wing molt

The process of molting replaces old worn-out feathers in an established sequence. In order to keep flying, most birds only molt a few adjacent feathers at a time in the primaries and a few in the secondaries. The molt is also symmetric—both wings lose the same corresponding feathers at the same time. Waterfowl molt all their flight feathers at once and are flightless for 2-4 weeks.

Most birds molt their wing feathers annually after completing nesting duties (autumn for most Northern Hemisphere breeders). Smaller birds  complete wing feather molt in a few weeks, medium birds may take several months. Very long-winged birds may molt only a portion of their flight feathers in a season, and may have several waves of molt going on in the flight feathers. A Wandering Albatross may take several years to complete wing molt and be aged by the state of molt and condition of the flight feathers up to five years of age.

The shape of the wing is altered by wing molt. Molt can create unusual notches where one feather is missing, the adjacent feather is 1/3 grown, and the next feather is 2/3 grown. When swifts molt their inner primaries the outer part of the wing can appear paddle-like. When the outer primaries of a pointed wing are molted it can give the appearance of a rounded wing.

Wing molt can also affect the flight style. With missing feathers, birds may have to flap more rapidly than usual. Soaring birds may have to flap more often than usual.


Feather wear

Old feathers become faded and tattered on the tips. At the end of the first year of a gull's life the wing feathers may become bleached to almost white and abraded to the point that the feather shafts are all that remains.


From head to toe

The length and width of the bill in relation to the head is usually obvious on a bird in flight. Neck length, trailing legs and feet, and tail length and shape are important to note on a bird in flight.

Figure 8: Long, broad, rounded wings, yes. But it is the long, sharp-pointed bill, neck tucked in a loop, and very long trailing legs beyond a short tail that identifies this Great Egret as belonging to the heron family.
Figure 8: Long, broad, rounded wings, yes. But it is the long, sharp-pointed bill, neck tucked in a loop, and very long trailing legs beyond a short tail that identifies this Great Egret as belonging to the heron family.

Figure 9: A duck, obviously. But the compact wing (short and broad) compared to other ducks, large blocky head and, especially, the long squarish tail make the silhouette of the Wood Duck unique.
Figure 9: A duck, obviously. But the compact wing (short and broad) compared to other ducks, large blocky head and, especially, the long squarish tail make the silhouette of the Wood Duck unique.

Shape of the tail

Often the true shape of the tail is most apparent in flight—especially if the bird flies directly overhead. On the other hand, pointed or forked tails may be held closed in flight. They then just look rather long and thin. When fanned open during a flying banked turn, square-ended tails will look rounded (Figure 12).

When the tail is folded (closed) the outer tail feathers are on the bottom and the central tail feathers are on the top of the feather stack. Any pattern on the outer tail feathers is fully shown on the undertail as the bird flies overhead. If you are viewing the top and back of the bird, the outer tail feathers are only discerned if the tail is fanned open.

The shape of the tail can be relatively long or short in comparison to the body. The shape of the end of the tail may take on the following appearances.

If all retrices (tail feathers) are the same length, the end of the tail is square. Sharp-shinned Hawks and European Starlings have square tails.

If the central tail feathers are longest and then shorten successively just slightly, then the tail appears rounded. Spotted Towhees and Western Scrub-Jays have rounded tails.

If  the retrices shorten from inside to outside in larger steps the tail is said to be graduated. Yellow-billed Cuckoos and Black-tailed Gnatcatchers have graduated tails.

If the central retrices are much longer than the outer retrices the tail appears pointed. Mourning Doves and Northern Flickers have pointed tails.

If the tail feathers lengthen gradually from inside to outside the tail is emarginate or notched. Purple Finches and Savannah Sparrows have notched tails.

If the outer tail feathers are much longer than the inner then the tail is forked. Common Terns and Barn Swallows have deeply forked tails.

Not all bird tails fit neatly into these categories. Some tails are almost square or slightly rounded. Is the Tree  Swallow's tail deeply notched or shallowly forked? Chimney Swifts have spiky little tail feathers. The tail of the Eared Grebe is not much more than fluff.

Figure 10: The Elegant Tern shows a forked tail.
Figure 10: The Elegant Tern shows a forked tail.

Figure 11: Boobies are sharply pointed on all four ends—including the pointed tail, as this Brown Booby shows.
Figure 11: Boobies are sharply pointed on all four ends—including the pointed tail, as this Brown Booby shows.

Figure 12: The square tail of this Western Kingbird looks rounded when fanned all the way open. The pattern of white outer vain on the outer tail feather is clearly seen from this underside viewpoint.
Figure 12: The square tail of this Western Kingbird looks rounded when fanned all the way open. The pattern of white outer vain on the outer tail feather is clearly seen from this underside viewpoint.




Flapping and flight path progression

Once you have observed the shape of the bird and the wings, you are ready to move on to how the bird uses them.

How a bird flies

Flapping flight is a complex combination of wing motion and angle, resulting in both lift and thrust. Airplanes have propellers or jet engines to provide thrust, so aircraft wings are fixed—they don't need to flap. The typical flight motion of a bird's wing can provide crucial identification clues.

In flight birds do not push their wings backward against the air as if swimming. The concave cross-section of the wing provides lift as the bird moves forward through the air. The faster the wing moves forward, the more lift is provided. Thus, on the downstroke the bird also pushes its wing forward. The faster a bird flies, the less it needs to push its wings forward, so this forward motion is most frequently seen on larger birds, especially soon after lift-off (Figure 13).

Figure 13: Birds push their wings forward on the downstroke—especially at slow speeds—as shown by the Tundra Swan on the bottom right.
Figure 13: Birds push their wings forward on the downstroke—especially at slow speeds—as shown by the Tundra Swan on the bottom right.

A full wing flapping cycle for Cackling Goose is show in Figures 14-18.

During the downstroke the wing feathers are fully extended, thus the air resistance is at its maximum (Figure 15). On the upstroke the bird rotates its wing to reduce drag (Figure 17). Therefore the upstroke is completed faster than the downstroke. In general, birds with larger wings will have slower wing beats, smaller birds faster.

Figure 14: Cackling Goose flight pose 1. Wings fully raised.
Figure 14: Cackling Goose flight pose 1. Wings fully raised.

Figure 15: Cackling Goose flight pose 2. Beginning downstroke. Wings flat. Feathers fully extended creating maximum wing surface.
Figure 15: Cackling Goose flight pose 2. Beginning downstroke. Wings flat. Feathers fully extended creating maximum wing surface.

Figure 16: Cackling Goose flight pose 3. Wings reaching fully down and pushed forward for maximum lift.
Figure 16: Cackling Goose flight pose 3. Wings reaching fully down and pushed forward for maximum lift.

Figure 17: Cackling Goose flight pose 4. Beginning to raise wing. Bent wrist, primaries open to reduce total air resistance of the wing.
Figure 17: Cackling Goose flight pose 4. Beginning to raise wing. Bent wrist, primaries open to reduce total air resistance of the wing.

Figure 18: Cackling Goose flight pose 5. Finishing the upstroke. Primaries partially folded and pointed back slightly, reducing drag. When the upstroke is finished the bird again will be as in flight pose 1 (Figure 14).
Figure 18: Cackling Goose flight pose 5. Finishing the upstroke. Primaries partially folded and pointed back slightly, reducing drag. When the upstroke is finished the bird again will be as in flight pose 1 (Figure 14).

Flapping frequency, angle, pattern

All birds have to move their wings as described above in order to fly. But within those parameters are a variety of styles.

Wing beat frequency can be fast or slow. In general, larger birds have slower wing beats. Ruby-throated Hummingbirds beat their wings about 50 times per second (range 40-80), much too fast to see. Likewise, the wing beats of many smaller birds are just a blur. You may be able to directly count (or estimate) the number of wing beats of larger birds in commuting flight. Herring Gulls beat their wings about 3 times per second and are easily counted. Double-crested Cormorants flap their wings about 5 times per second. You may not be able to reliably estimate the 9 wing beats per second of a Northern Flicker, but you can still see the individual strokes, though too fast to count; they are not a complete blur.

The geese we looked at (Figures 14-18) had rather deep wing stroke angles. They raised their wings to more than 45 degrees above the body plane and lowered them to about 45 degrees below the horizontal. On the other hand, a Spotted Sandpiper flying across a stream flies with its very stiff and arched wings mostly below the horizontal—perhaps +15 to -35 degrees.

All that constant flapping brings with it an energy cost. Thus, to conserve energy, many birds fly with with intermittent bursts of flapping and a pause. Flap-glide is used by larger birds. They will flap a few times and then glide on open wings. Jays are about the smallest birds that use this technique. On birds smaller than jays the wing has too much drag. Thus, smaller birds, such as goldfinches, use a flap-bound style of flight. They fly upward with a burst of wing beats and then they fold their wings completely, quickly losing altitude. This often creates a bounding roller-coaster line of flight. In general, flap-glide flight is slower than flap-bound.

Some species use a hybrid approach. They flap several times, then partially fold their wings with shoulders out slightly and wingtips bent clear back by the tail. American Robins (Figure 28), Tree Swallows (Figure 30), and Cassin's Kingbirds fly in this manner.

How many times does a bird flap before it pauses? And how long is it between each flap-bound series? The average sometimes varies between even closely related species. Practice counting the wing strokes if possible.

Another flapping characteristic, the wing beats may be noticeably stiff (shearwaters, hummingbirds) or flexibly graceful (swans, cranes).


Wind speed and direction

Flight style will be altered with wind. A bird flying into the wind may flap more frequently and with deeper wing strokes than one flying with the wind. On the other hand, soaring birds may glide more and flap less tacking across stronger winds.


Flight progression

Imagine a line tracing out the flight path of the bird you are watching. If it is a crow or American Robin in commuting flight, that line—the flight path—is probably quite straight and level. If it is an American Goldfinch the flight might be straight side-to-side, but undulating—rising and falling considerably. And if it is a Barn Swallow it may be swooping and twisting and turning—moving about in all three dimensions.

Now mark on your bird's imaginary flight path line the location of the wing beats (Figures 19, 26, 27). If it was an American Crow the individual wing beats are evenly spaced across the flight path line. However, if it is an American Goldfinch, the wing beats are in a burst—too fast to count. Not only that, but the wing beats create the upward portion of the rising bound. When the wing beats stop, the goldfinch starts falling until it flaps again.

Is the flight progression straight, undulating, swooping, zigzag, or erratic? Is the flight high in the air, low over the ground, through the trees, or at tree top level?


Hard-to-explain qualities of flight

There are still some subjective flight characteristics that are hard to describe exactly and quantify. So we have descriptive comparative words we use to try to communicate an added dimension to some bird's flight. And these descriptions can often be quite effective in leading to a correct identification. For instance, flight can appear rapid or leisurely, strong or weak, direct or aimless, labored or graceful, mechanical or fluid. The indirect or aimless way a Bushtit flies as it laboriously crawls slowly across the airspace between bushes, as its too-long tail seemingly pushes it off course, must surely be the inspiration for Charles Schultz's little bird “Woodstock” in the “Peanuts” comic strip.


Flocking behavior

Not all birds fly in flocks. But those that do may show flocking behaviors ranging from a highly organized 'V' or tight oval to loose clumps or straggling lines. When a predator suddenly appears, the spread out and disorganized clumps of birds may converge into a single tight ball all flying in unison. When the danger passes the one flock may break apart into several smaller groups, seemingly at random.

While we might think of flocking birds as consisting of just one species, it would not be unusual for several species of ducks or shorebirds to join into a flock for protection.  During migration it is not unusual to see a line of Common Murres at sea being led by a Rhinoceros Auklet, Long-tailed Duck, Green-winged Teal, or other species... at least for a while.




Other identification clues

Plumage coloration

It is often possible to get a good enough view to identify a flying bird using the same traditional field marks as on a perched bird: eyebrow, breast streaking, white tail corners, wing patches, etc.

From front to back note length, shape and color of bill, then color or contrasting shades on side of head and neck, throat, breast, belly, vent, under tail coverts, and tail pattern. Look for wing markings and note color of the under wing linings, primaries, and secondaries. At the very least, note any contrast between dark and light areas.

Call notes

Many birds have short, distinctive call notes in flight. In fact, it is often the call note that first attracts our attention to a bird flying high overhead.

Even if you don't recognize the call, write down a description. Perhaps you'll hear it again later and get a good view and be able to finally identify the bird. Many songbirds migrate at night and may have call notes quite unlike their day time call notes given on the ground.

Here are the first questions to ask when you hear a bird call or song. First, how many syllables do you hear? What is the relative pitch of the call? Is it a level pitch or does it drop or rise? What is its quality—Whistled? Chirping? Rough? Trilled? Musical?




Some help along the way

The following books will help in your quest to identify birds in flight. But each has additional wonderful features to help you grow in your overall birding skills.

Jonathan Alderfer and Jon L. Dunn. 2007. National Geographic Birding Essentials. When we started watching birds most of us learned on our own. It took years or decades before I understood all the parts of birds, molt, status and distribution, and field craft. Wouldn't you like to have a basic understanding all in one place? This is it! It says it is for beginners to become better birders. Make no mistake, it will help birders of all skill levels fill in any missing aspects of bird watching techniques. This book is essential for your birding library.

Kenn Kaufman. 2011. Kaufman Field Guide to Advanced Birding. This is about 70% new material from the 1990 Peterson Field Guide series classic of almost the same name. Again, while this book says it is for advanced birders, it covers the same material that Birding Essentials above says is for beginners. Both are correct.

David Allen Sibley. 2014. The Sibley Guide to Birds, Second Edition. You may already own the 2000 classic. It was the first popular field guide to show all birds—even passerines—in flight. It does not describe flight, however, for most species. This Second Edition has more birds in flight depicted and the newest taxonomy. Get the 2nd printing of the Second Edition, as the first printing was over-saturated on colors and the text was too small and pale.

Pete Dunne. 2006. Pete Dunne's Essential Field Guide Companion. Structure and behavior are the emphasis used in this book to identify birds. Consider it a complete field guide without any illustrations or maps—only words! The descriptions of flight are often overly wordy and flowery, but they tend to get the point across. I didn't know what to make of it at first, and it sat unused on my bookshelf for far too long. But I find myself coming back to it for the behavioral and flight descriptions—and when I'm looking for a memorable quote on a specific bird!

Donald and Lillian Stokes. 2010. The Stokes Field Guide to the Birds of North America. This photographic field guide starts each species account with shape before plumage considerations. Exactly correct. And it includes subspecies! Each account includes a flight description, but it is a bit uneven in whether it describes flight style or visible plumage attributes in flight. Nevertheless, this is probably the first field guide to attempt to cover flight in this manner.




Putting it all together

Following is a one-page “Bird flight style identification worksheet.” It takes all the identification clues and circumstances and allows one to “fill in the blanks” in order to describe the flight of a known-identity bird. It is great practice to help one observe birds in flight.

The steps are basically these.  Pay attention to 1) wing, tail, and body shape, 2) wing flapping pattern, 3) flight path, 4) colors or patterns (traditional field marks), 5) flocking behavior, and 6) flight calls.

You will rarely have the time and circumstances to fill in all the blanks on the worksheet. That's okay. Each time you see a species write down what you notice, perhaps concentrating on a different feature each time. Write them down on separate worksheets—don't use one worksheet per species. Each bird is an individual and individuals may not always fly exactly the same. So record each flight observation on a different worksheet.

Write your observations down!—It will help reinforce your observations so that you learn birds in flight more quickly. Soon you'll be instantly recognizing the common birds in your area by the way they fly. Also, your attention will be drawn to less common birds exactly because you don't recognize their flight yet.

Kenn Kaufman recommends that when we have identified a perched bird, we don't put our binoculars down the moment it flies—keep watching it as it flies away! How does it fly? What identifying field marks are visible the farthest?

Learning birds in flight is really faster than one-at-a-time because you'll quickly begin to recognize flying birds to larger units, “oh, that's a woodpecker,” “that is a flycatcher,” “that is a blackbird,” and “that is a tern.” With that knowledge you can zero in on any observable plumage characters, any vocal clues, your knowledge of local status and distribution, to identify it to species level. Then observe for any flight style characteristic that separate it from similar species.




Bird flight style identification worksheet

Date:
Location:
Observer:
Weather:
Wind speed and direction:

Species:
Age/plumage:
Flight direction of bird:

Flight style:
Commuting, soaring, gliding, landing, taking off, hovering, chasing, fleeing, courtship, feeding

Silhouette & Wing Shape
Draw and describe head, bill, body, neck, tail, wing position, wing tip shape, arm vs. hand length, flatness, leading edge, trailing edge. Shade obvious areas of dark and light.










Flapping & Flight path
Describe angle above and below horizontal, wing beat frequency and pattern, wing stiffness. Draw progression, height above ground, speed, and location of flaps. Describe overall impression of flight.








Call notes
Flight notes or other sounds


Other behaviors or notes:





Part 2: Flight style descriptions

West Coast Shearwaters

My first real effort at describing birds in flight was explaining how I was able to identify shearwaters at extreme distances on pelagic trips. It turns out that only flight path and flapping pattern are necessary to identify the common shearwaters in their flap-glide flight style. Plumage differences are only necessary for rarer species.

Figure 19: Flapping and flight paths of West Coast Shearwaters
Figure 19: Flapping and flight paths of West Coast Shearwaters




European Starling versus Cedar Waxwing

The human brain is very, very good about instantly recognizing familiar items (people or birds) with only brief or distant views. The human brain is really, really bad, however, about letting you know how it does it.

In the summer of 2010 I spent considerable time trying to figure out how to separate flying European Starlings from Cedar Waxwings. It wasn't that I was having trouble with the ID. In fact, it only took about 2 seconds. The trouble was, I couldn't figure out how I was doing it! These nearly identical-shaped birds were usually only silhouettes flying high against bright overcast skies. And the flight style also is basically the same. Both give 5-7 quick strong flaps and then fold the wings completely—very typical flap-bound flight.

Recently I made several measurements of photos of these birds flying overhead. The ratio of wingspan to total length on both birds is about the same. The heads project about the same relative distance forward of the leading edge of the wing.

Two things were different in the silhouette. The waxwing's wing was relatively narrower (shorter secondaries). This gave the appearance of a longer, thinner, more pointed wing, and it gave the appearance of a longer tail. The starling's wing was wider and appeared shorter and more triangular. The wider secondaries gave the appearance of a shorter tail.

Another physical attribute contributed to the apparent wing differences. The leading edge of the waxwing's wing was almost perfectly straight, adding to its longer look. On the other hand, the wrist of the starling bumped out gently—it wasn't obvious, but it gave the leading edge of the wing an ever-so-subtle curve, adding to its shorter, triangular look.

Even though both had a similar flap-bound flight, the starling's flight was more level; the waxwing's flight was slightly more undulating. This showed up in the flocking flight as well as individually.

Figure 20: Flight shapes of European Starling (left) and Cedar Waxwing (right). Purposely not to scale (the Starling in life is slightly larger).
Figure 20: Flight shapes of European Starling (left) and Cedar Waxwing (right). Purposely not to scale (the Starling in life is slightly larger).



Crows and Ravens in flight

These all-black birds give many people difficulty in identification. However, they have a different silhouette and different style of flight.

American Crows (Figure 24) have rather short broadly rounded wings, with the wrist pushed forward slightly. The bill is pointed and head is obvious on short neck. The tail is medium length and rounded at the tip.

Common Ravens (Figure 25) have a straighter leading edge on the wing (less obvious wrist) and the hand is longer and wing more pointed. The bill and neck are longer. The tail is longer and wedge-shaped—it would be pointed, but the central tail feathers are blunt.

The flight of the crow during relaxed commuting flight is a steady, deep flapping, about 3-4 wing beats per second raised and lowered to +25 and -45 degrees (Figure 22). [When accelerating this changes to 5-6 wing beats per second and +45 to -45 degrees.] The wings make an obvious rowing motion—a circle or ellipse—forward and down, faster back and up, (an almost imperceptible pause) and repeat (Figure 21). Crows sometimes glide briefly on stiff wings held slightly above the horizontal (Figure 22).

The flight of the raven is flap-glide, with a variable number of flaps between glides of various lengths. Wing beats are about 3 per second raised and lowered to +35 and -35 degrees. The wing appears to move more up-and-down, rather than in a circle, as the crow. The longer hand is flexible. Soaring, the wings are held out horizontally. The whole impression is of a relaxed, hawk-like flapping (Figure 23).

Both of these are roadside birds in agricultural (crow) and wilderness (raven) areas. I used to get a lot of ID practice as I drove from the valley over the mountains to coast or desert. The difference in flight style is obvious whether they are flying perpendicular to you or straight at you (or away).

Figure 21: Wing movement of American Crow in flight. Down-and-forward, up-and-back in a steady rowing motion.
Figure 21: Wing movement of American Crow in flight. Down-and-forward, up-and-back in a steady rowing motion.

Figure 22: Head-on view of flapping angles of American Crow. Brief glides on slightly upraised wings.
Figure 22: Head-on view of flapping angles of American Crow. Brief glides on slightly upraised wings.

Figure 23: Head-on view of flapping angles of Common Raven. Soars and circles on rather flat wings.
Figure 23: Head-on view of flapping angles of Common Raven. Soars and circles on rather flat wings.

Figure 24: Flight shape of American Crow.
Figure 24: Flight shape of American Crow.

Figure 25: Flight shape of Common Raven.
Figure 25: Flight shape of Common Raven.



Late autumn sparrows in the weedy marsh

Observations from Fernhill Wetlands, Forest Grove, Oregon on October 11, 2010.
Path on dike along edge of weedy pond that had been dry since late spring. Dry pond filled with reed canary-grass, some clumps of wild rose and willows.

Savannah Sparrows: fed on ground on path of dike. Either flew far off over the reed canary-grass and landed, or flushed up into the willows along the dike. From there would often flush again back, around behind me on the dike. Flight: goldfinch-like with 3-4 flaps and folded wing [flap-bound] with undulating flight. General overall color: straw yellow. Flight note: “seep” slightly rising at end.

Song Sparrow: flushed short distance, often into base of willow clump or reed canary-grass. Flight: low, fluttery with zealous tail pumping. Response to pishing: intense interest, coming closer, and eventually perching in top of grass or bush. General overall color: deep rusty brown [Rusty Song Sparrow subspecies]. Call: “chimp.” Flight note: high-pitched “seee.”

Lincoln's Sparrow: shy and hiding. Primarily low in the reed canary-grass along the dike. Flushed a short distance farther out into reed canary-grass where they hid. Flight: low in fluttery flight with tail pumping. Response to pishing: stayed hidden if previously flushed. If not previously flushed may pop up a foot as if startled, somersault back down, and flush frantically away low through the weeds 5-15 feet and stay hidden with no further response. General overall color: gray-brown. Call: “tic” or “chap.” Flight note: high-pitched, slightly buzzy “z-z-ee,” similar to Song Sparrow but buzzy rather than clear.




Flight style comparison: Red-winged Blackbird and  Brown-headed Cowbird
Forest Grove, Oregon, July 5, 2010 and Hillsboro, Oregon, July 19, 2011.

Red-winged Blackbird: 7 flaps then folded [flap-bound]. Undulating, but not strongly so. Pot-bellied, pinched tail base. Slightly rounded wings.

Brown-headed Cowbird: 2 flaps, folded, then 3 flaps, folded [flap-bound]. Uneven, slightly undulating flight. Faster flight than Red-winged Blackbird. Slimmer. More pointed wings.

Figure 26: Flapping and flight path of Red-winged Blackbird (top) and Brown-headed Cowbird (bottom).
Figure 26: Flapping and flight path of Red-winged Blackbird (top) and Brown-headed Cowbird (bottom).



Flight of Red-breasted Nuthatch

Observation of a male and female flying back and forth to feeder on April 10, 2011 at Beaverton, Oregon.

In flight the male and female separated by blacker crown on male, darker central tail feathers with contrasting white outer tail feathers. Female grayer with less contrast.

Flight progression strongly undulating with bursts of very quick wing beats, flight path rising quickly, then falling as wing folded.

Pudgy body, short neck, pointed bill, short broad tail, short, rounded wings.

Figure 27: Flapping and flight path of Red-breasted Nuthatch.
Figure 27: Flapping and flight path of Red-breasted Nuthatch.




Flight of American Robin
July 1 and 19, 2011, Portland and Hillsboro, Oregon.

3-5 rapid flapping bursts, partially folding wings back toward tail. Wing beat frequency is not unusually fast (5 beats per second?), but individual wing stroke fast, flicking, mostly below the horizontal. Flight path level. Broad, rounded wings, rather straight leading edge, more rounded trailing edge. White fluffy under tail coverts and vent contrasting with darker belly and tail.

Figure 28: Outline of American Robin flapping and partially closed glide.
Figure 28: Outline of American Robin flapping and partially closed glide.




Courtship flight of American Goldfinch
July 6, 2011 Beaverton, Oregon.

Flying rather high in large horizontal circle, slowly, with wings and tail spread widely. Shallow, fluttery wing strokes. Wings appear very broad and rounded. Pale under wing coverts contrast with black primaries. White vent and under tail coverts. Spread tail shows black and white feathering. Singing constantly.

Figure 29: Drawing of American Goldfinch in overhead display flight.
Figure 29: Drawing of American Goldfinch in overhead display flight.




Tree Swallow

Cooper Mountain, Beaverton, Oregon, July 6, 2011.

Feeding flight: graceful glides, banking, and turns, interspersed irregularly with snappy deep flapping on broad-based but flexible pointed wings.

Commuting flight: more direct, intersperses several flaps with short pauses or brief glides with wings partially closed and folded so that the tips of  the wing are back near the tail.


Forest Grove, Oregon, July 19, 2011.

High relaxed commuting flight: Almost every flap ends in a partially closed glide. Sharply forked tail evident. Head barely protrudes as wide wings held forward at wrist. Additional gliding with wings angled down slightly.

Figure 30: Outline of Tree Swallow flapping and partially closed glide.
Figure 30: Outline of Tree Swallow flapping and partially closed glide.




Flight of Wilson's Snipe

Fleeing: Jumps into quick zigzagging or twisting flight on short pointed wings held forward at the wrist and a harsh scraping call. Sometimes flies rather high and circles around, losing some of the twisting but still fast with rapid wing beats.

Courtship flight: Perhaps 250-350 feet in the air transcribes a large horizontal circle perhaps 400 feet across. Very fast flight, pointed wings held forward at wrist. Low hollow whistle produced by the tail feathers hu-hu-hu-hu-hu-hu-wu-wu-wu-wu-wu... louder then fading with Doppler effect as circle transcribed.




Black Oystercatcher

Commuting flight: Strong rapid flapping +30/-40 degrees, on bowed wings, low over the waves or along rocky shore. Usually loud single piping whistled notes in flight.

Courtship chasing flight: Two birds in slow, high (to 60 feet above waves, shore) flight with quivering wings, flapping with wings held in very high “V” +75/+50 degrees. Normal flight call run together into accelerating crescendo and then fading. [I have not seen this particular flight display described anywhere else. It may be related to the so-called “butterfly flight,” which is described as slow, exaggerated deep flapping.]