From the Cornell Lab of Ornithology:
Are you amazed at how quickly birders can identify birds? Actually, it’s just like getting to know your human neighbors. When you move into a new neighborhood everyone is a stranger, but soon you recognize people based on their characteristics, such as habits, shape, styles of walking, and the places where you see them.
Paying attention to individual differences can help you identify birds, too. You can recognize many birds simply by noting their shapes, even if seen only in silhouette. Other useful characteristics are a bird’s posture, size, flight pattern, and the kind of habitat in which the bird was seen.
Start by learning to identify general groups of birds– warblers, flycatchers, hawks, owls, wrens–whose members all share certain similarities. As your observation skills improve, familiarize yourself with the field marks–colored or patterned areas on the bird’s body, head, and wings–that help distinguish species.
Use the following features to help you:
Birds in the same general group often have the same body shape and proportions, although they may vary in size. Silhouette alone gives many clues to a bird’s identity, allowing birders to assign a bird to the correct group or even the exact species.
Pay attention to the following:
- body shape
- proportions of the head, legs, wings
- tail shape
- length of the bill
In order to describe a bird, ornithologists divide its body into topographical regions: beak (or bill), head, back, wings, tail, and legs. To help with identification, many of these regions are divided still further. This diagram of regions of the bird’s body shows some of the commonly used descriptive terms.
Birds display a huge variety of patterns and colors, which they have evolved in part to recognize other members of their own species. Birders can use these features – known as field marks – to help distinguish species.
Pay particular attention to the field marks of the head and the field marks of the wing.
Field Marks of the Head
When identifying an unknown bird, the following field marks of the head are particularly important:
- Eyebrow stripe(or superciliary line, above the eye)
- Eyeline(line through the eye)
- Crown stripe(stripe in the midline of the head)
- Eyering(ring of color around eye)
- Throat patch
- Color of the lore(area between base of beak and eye)
- Whisker mark(also called mustache or malar stripe)
- Color of upper and lower beak
- Presence or absence of crest
Beak shape and size are also important identifying characteristics.
Field Marks of the Wing
In a few groups, notably warblers and vireos, the presence of wing markings gives positive identification even if the bird is in non-breeding plumage. In other groups, such as flycatchers and sparrows, the absence of any wing markings may be an important distinguishing characteristic. Note the presence or absence of the following:
- Wing patches
Posture clues can help place a bird in its correct group. Watch an American Robin, a common member of the thrush family, strut across a yard. Notice how it takes several steps, then adopts an alert, upright stance with its breast held forward. Other thrushes have similar postures, as do larks and shorebirds.
Certain bird groups have distinctive vertical posture when perched on a branch. Flycatchers, hawks, and owls typically sit in an upright pose with tails pointing straight down.
Other birds perch horizontally on vegetation with tails pointing out at an angle, for instance vireos, shrikes, crows, and warblers.
Distant perched crows and hawks may look alike, but paying attention to their different postures may help to tell them apart. The Red-tailed Hawk perches upright, whereas the similarly-sized American Crow perches horizontally.
Once you have assigned a bird to its correct group, size can be a clue to its actual species. Be aware, though, that size can be difficult to determine in the field, especially under poor lighting conditions or at a distance. Size comparisons are most useful when the unknown bird is seen side-by-side with a familiar species. In the absence of that, you can use the sizes of well-known birds, such as the House Sparrow, American Robin, and American Crow, as references when trying to identify an unfamiliar bird.
A crow-sized woodpecker would be a Pileated, but one the size of a sparrow might be a Downy Woodpecker (or a Ladder-backed Woodpecker in the Southwest).
Confusing Coloration: A yellow-and-black finch smaller than a sparrow is probably an American Goldfinch. Evening Grosbeaks have similar colors and patterns, but are almost robin-sized.
Sometimes you need two reference birds for comparison. A Cedar Waxwing is bigger than a sparrow but smaller than a robin. A Blue Jay is larger than a robin but smaller than a crow.
Most birds fly in a straight line, flapping in a constant rhythm, but certain bird groups have characteristic flight patterns that can help identify them. Birds of prey may be identified by the characteristic way they hold their wings when viewed flying toward you. Here are some useful identification tips:
Up-and-down Flight Pattern
Finches exhibit a steep, roller-coaster flight, whereas woodpeckers generally fly in a pattern of moderate rises and falls.
Flapping Versus Gliding
Flying accipiters such as Sharp-shinned Hawks, Cooper’s Hawks, and Northern Goshawks typically make several wing flaps followed by a glide. Buteos, such as the Red-tailed Hawk, are usually seen soaring. Dashed lines indicate flapping, solid lines soaring.
Crow Versus Raven
Flight patterns can sometime distinguish similar species. The American Crow, for instance, flies with deliberate, flapping wingbeats. The similar Common Raven often alternates flapping with hawk-like soaring.
Head-on Flight Profiles
Head-on flight profiles may also give identity clues. Soaring Turkey Vultures may look like hawks, but they hold their wings in a shallow V-shape, whereas most hawks and eagles hold their wings out flat. Black Vultures also have a flatter, more hawk-like profile. Northern Harriers hold their wings in more of a V-shape, but their slow, flapping flight near the ground generally gives away their identity. Notice how the Bald Eagle’s profile is even more flat than that of a typical hawk, such as the Red-tailed Hawk.
In general, each species of bird occurs only within certain types of habitat. And each plant community – whether abandoned field, mixed deciduous/coniferous forest, desert, or freshwater marsh, for instance – contains its own predictable assortment of birds. Learn which birds to expect in each habitat. You may be able to identify an unfamiliar bird by eliminating from consideration species that usually live in other habitats. (Be aware, though, that during spring and fall migration birds often settle down when they get tired and hungry, regardless of habitat.)
Below are some common birds of common plant communities. As you’ll see, bird groups such as sparrows, wrens, hawks, and warblers are common to each community, but the actual species differ depending on the habitat.
Agricultural fields no longer used for farming form an “old field” habitat as they slowly revert to forest. In the Northeast and the Mid-Atlantic states, the original grasses are replaced with plants such as goldenrod, mullein, asters, and brambles (blackberry). Thickets of woody shrubs – such as honeysuckle and multiflora rose – develop, mixed with small trees such as red cedar, black locust and hawthorn. Birds found there include Field Sparrow, House Wren, Red-tailed Hawk, and Blue-winged Warbler.
Mixed Deciduous / Coniferous Forest
In a broad band stretching from the Great Lakes region eastward to New England and the Maritime Provinces of Canada, the southern deciduous woodlands and the coniferous forests of the north meet and intermingle. There broad-leafed trees such as oaks, hickories, beeches, and maples mix with conifers such as spruces, firs, and hemlocks. Birds that live there include Winter Wren, Northern Goshawk, White-throated Sparrow, and Black-throated Green Warbler.
A freshwater marsh is a treeless wetland whose shallow water supports dense stands of mostly emergent plants (rooted in mud but with most of their foliage above water). Marshes are found throughout North America, often forming when ponds and shallow lakes fill in, although beavers may also play an important role in their formation. Typical vegetation includes cattails, bulrushes, sedges and reeds. In deeper pools submerged and floating aquatic plants occur, including water lilies, pondweed, arrowhead, duckweed, smartweed, bladderwort, pickerel-weed, water-shield, and sweet flag. Bands of shrubs such as alder and willow occur at drier marsh edges. Swamp Sparrow, Northern Harrier, Marsh Wren, and Common Yellowthroat are typical residents.