Gulls are a group of birds that can challenge birders of all levels. Lay people often refer to them generically as seagulls, but as you'll see (in this and future posts), the diversity within and between species of gulls begs greater specificity. Watch a group of gulls for any length of time, and you'll witness this first-hand.
Gulls vary widely in size and coloration, with young birds of a given species taking from one to four years to obtain adult plumage. Young gulls are usually browner overall, and look crisper with age.
A common gull found practically continent-wide is the Ring-billed Gull. Adult birds (above photo) have yellow legs, yellow bills marked with a ring of black, and black-tipped wings. When standing with wings folded, small white spots are visible on those black tips.
First-year birds are darker and have black-tipped bills, instead of an adult's signature ringed-bill. The above photo shows two adults with a first-winter bird. The gray back on this young bird is beginning to come in.
Next time you spot a group of parking lot, restaurant, ocean or lakeside gulls, stop and see if you can pick out an adult and an immature Ring-billed Gull.