BIRDING

Wingspans of North American gulls vary greatly, so use them as an ID clue.

For more gull ID tips and hotspots, go to audubon.org/birding.

4 Key Field Marks

Gulls of many species sport a similar color scheme of white, black, and gray. A few key characteristics will help you tease them apart.

EYES While all juvenile gulls are dark-eyed, the eyes of adults are dark or dusky on some species, and bright yellow on others.

LEGS These can be light pink, reddish, yellow, greenish, or black on adults. On young birds, leg color may be less helpful.

BILL A