For those of you who enjoy knowing about avian phylogeny, there's an
interesting paper in the latest Auk.

Given, A. D., J. A. Mills, and A. J. Baker. 2005. Molecular evidence
for recent radiation in southern hemisphere masked gulls. Auk 122:
268-279.

In this paper, the authors conclude that the Black-headed Gull is a
member of a clade (group of related species) consisting otherwise of
southern-hemisphere gulls (South America, Africa, Australia, New
Zealand), many of which are "masked" (or "hooded," both referring to
the dark heads of some species). Some of the species have secondarily
lost the dark head and are white-headed, but if you've seen them, you
can easily see that they're related to the black-headed or
brown-headed or gray-headed species, and it's thought that the early
evolution of gulls involved dark-headed birds, with white heads
coming later.

This finding indicates that not only aren't the Black-headed and
Bonaparte's each other's closest relatives, but they're not closely
related at all, even though they are superficially similar in the
field. The phylogeny of the other "masked" gulls (e.g., Laughing,
Franklin's and others) has not been worked out, but they also are not
considered part of the southern dark-headed clade.

Dennis
--
Dennis Paulson, Director Emeritus phone 253-879-3798
Slater Museum of Natural History fax 253-879-3352
University of Puget Sound e-mail dpaulson at ups.edu
1500 N. Warner, #1088
Tacoma, WA 98416-1088
http://www.ups.edu/biology/museum/museum.html