As you can see from one of the postings, it sounds as if Ross' Gulls feed
mostly in the ways other gulls feed. The few I have seen did nothing to
disabuse me of that notion. I would guess that their relatively short neck
and short bill (and relatively short legs? someone needs to check
measurements in Dwight's "Gulls of the World") are adaptations to extreme
cold. Endothermal ("warm-blooded") organisms (primarily birds and mammals)
generate heat proportional to the volume of their body and lose heat
proportional to their surface area. A lower surface-area-to-volume ratio is
thus an adaptation to conserve heat in an organism that lives in cold
climates. Shorter extremities (think of an Arctic Tern's bill, neck, and
leg length in comparison with a Common Tern) reduce the surface area of the
bird relative to its volume and, in the case of bill and legs, reduce the
area of unfeathered parts that lose heat.

Heat is also lost through the eyes, which might thus be smaller in
high-latitude birds, although sun glare during the breeding season (or
around ice) could also explain a smaller eye. If the bird were nocturnally
oriented, I would expect a larger eye. Ross' Gulls winter at very high
latitudes where there is little light, so they may be adapted to feeding
under those circumstances. Comparing photos in the Audubon Master Guide,
Ross' indeed looks large-eyed in comparison with Bonaparte's.

And can anyone explain the pointed tail in this species, in a group in
which tails are usually slightly rounded, square or notched? It's
interesting that pointed tails are fairly common in shearwaters, but I
don't see much in common between them and Ross' Gulls. Then that gets you
into the question of why noddies have pointed tails while other terns have
forked tails.....surely there's an aerodynamic explanation lurking out
there.

Dennis Paulson phone: (206) 756-3798
Slater Museum of Natural History fax: (206) 756-3352
University of Puget Sound e-mail: dpaulson at ups.edu
Tacoma, WA 98416