Field Marks

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