Wednesday, October 20, 2010

Ring-billed Gull

Ord in 1815 first described the Ring-billed Gull from the Delaware River near Philadelphia, hence its scientific name, Larus delawarensis.  A great book is Words for Birds, which describes the origins of American bird names, and can be obtained at bargain prices from the the link on the right of this page. The species is quite common across most of the mid-section of North America. 

The Ring-billed Gull is abundant in Minnesota.  They inhabit garbage dumps,  fields, and our numerous lakes. Its hard to believe this gull was almost exterminated by the 1920s. Although still often considered a pest, obviously the species has recovered. Even now, however, control efforts are occasionally attempted. Ring-billed Gulls eat about anything, including insects, earthworms, fish, rodents, and grain. The birds in these photos foraged in a park for picnic scraps in Stillwater, Minnesota.

This species is usually monogamous.  However, when females outnumber males, the males will fertilize females who will then form pairs with other females.  Both females in these pairs lay clutches in the same nest and raise the young (Ryder 1993).

The Ring-billed Gulls in these photos appear to be adults in winter plumage.  This gull takes three years to reach adult plumage.  First-year birds are dusky.  Second-year birds lack the large spots that you can see on the wing tips in the photo above. As you can see by the differing amount of streaking on their heads, even birds in similar plumage, as in these photos, can be variable. Add to that variation the various plumages through which the gulls pass, and you can see that identification can be tricky.  Gulls of North America, Europe, and Asia (inexplicably very expensive) and Gulls of the Americas are good books for gull identification.  Note the deformed lower bill on the photo below--the lower mandible is longer than the upper one.

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