Using Field Marks to Identify Birds
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:
- Wingbars
- Wing patches