Bird ID Skills: Field Marks

Once you’ve looked at Size & Shape, Color Pattern, Behavior, and Habitat to decide what general type of bird you’re looking at, you may still have a few similar birds to choose between. To be certain of your identification, you’ll need to look at field marks.

Field marks are the distinctive stripes, spots, patterns, colors, and highlights that birds have in such abundance and variety. Birds developed these patterns for many reasons, but one way they use some of these markings is to recognize members of their own species. And bird watchers can use them for the same purpose.

When you dive into the world of field marks, it helps if you learn a little bird anatomy. Trust us, it’s a lot easier to notice what color a bird’s malar stripe is if you know it’s that line angling back from the bird’s chin, separating the cheek from the throat. You’ll know the difference between an alula and a greater secondary covert in no time.

Ornithologists talk about parts of a bird by dividing its body into topographical regions. The main divisions are beak (or bill), head, back, throat, breast, wings, tail, and legs. Many of these regions are divided still further.

Field Marks of the Head

You’ve probably already taken a close look at your mystery bird’s head by now, if only to note its beak shape as a clue to its group. Make it a habit to note these useful field marks as well (listed clockwise starting from the eyebrow stripe):

You’ve probably already taken a close look at your mystery bird’s head by now, if only to note its beak shape as a clue to its group. Make it a habit to note these useful field marks as well (listed clockwise starting from the eyebrow stripe):

• Eyebrow stripe (or superciliary, line over the eye)
• Eyeline (line through the eye)
• Whisker mark (also called mustache or malar stripe)
• Throat patch
• Color of upper and lower beak
• Color of the lore (area between base of beak and eye)
• Crown stripe (stripe in the midline of the head)
• Eyering (ring of color around eye)
• Presence or absence of crest
• The color of the eye itself (iris) can also be very useful

Field Marks of the Wing

Birds’ wings are another great place to pick up clues to a bird’s identity. In a few groups, including warblers and vireos, wing markings can give you a positive identification even if the bird has molted out of its colorful breeding plumage. In other groups, such as flycatchers and sparrows, the absence of wing markings may be important. Ducks, shorebirds, raptors, among others, often show distinctive markings in flight, when their wings are spread and new feathers are exposed. Keep an eye out for these field marks:

• Wingbars (stripes across the folded wing)
• Wing patches (blocks of color on the wing)
• Wing lining (the feathers covering the underside of the wing)
• Primaries (the long flight feathers on the outer half of the wing)
• Secondaries (the flight feathers on the inner half of the wing)
• Speculum (the patch of colored secondaries that helps identify many ducks)
• Wing tips