Monday, 16 March 2015

B.O.T.D. Heermann's Gull

Heermann's Gull (Larus heermanni)


What a relief it is to lay eyes upon a Heermann's gull! Here is a gull that is easy to identify, its dark body handsomely set off by a blood-red bill and, in breeding garb, an elegantly white head. Even the chocolate-brown young are easy to identify from other gulls.

Both young and adult Heermann's clearly diverge from the "mainstream" appearance of our white-bodied (and sometimes black-headed) North American gulls. And they are exotic in habits as well as looks. They breed in spring, primarily in northwestern Mexico - where the main task of the "incubating" parent is not to warm the eggs but to shade them from the blazing sun. After breeding, Heermann's gulls and their young disperse northward from Mexico across the western U.S., reaching British Columbia by July and remaining along the Pacific coast until they move south to nest again.

No one knows how Heermann's gulls came to reverse the usual pattern of southward dispersal after breeding, but the food-rich West Coast is a natural destination for any gull breeding nearby. Nine other species of gulls "winter" there as well - eight of them migrants from farther north. In any event, the Heermann's contrary habits clearly meet its needs quite nicely, and its summer tourism provides a welcome sight on our western beaches.