{Byron,

An interesting paper (Divoky, G.J. 1976.The pelagic feeding habits of Ivory
and Ross' Gulls. Condor 78:85-90) documents juvenile arctic cod and
amphipods as major food items for both Ivory and Ross' Gulls in the Bering
Sea and Arctic Ocean in northern Alaska in late summer and fall. Most gulls
observed in this study obtained prey by dipping from flight. Divoky
outlines the different niches exploited by these two gulls, especially in
wintertime. Apparently Ivory Gulls winter mostly at the edge of the ice
pack in the Bering Sea. This is "annual sea-ice" with a poorly developed
zooplankton fauna, because it is of ephemeral occurrence. Ivory Gulls feed
at the edge of this ice on juvenile arctic cod and amphipods. Ross' Gulls,
on the other hand, winter mostly north of the Bering Strait in the Arctic
Ocean. Here the ice is "old," and apparently has a well-developed, if
simple fish and invertebrate fauna associated with it-arctic cod and
amphipods being important members of this community. Apparently, these
organisms are concentrated near the edge of the ice, as ice offers
protection for this fauna. Thats where the gulls are.

My question is how Ross's Gulls forage in the darkness or near-darkness
that envelops this part of the world for months on end?

My experience with the Ross' Gull at McNary Dam (28 November, 1994)
included observing it dip into the water twice after a brief hovering
flight to snatch and instantly swallow small fish (appeared a little longer
than the bill of the gull.). On both occasions, the gull was pursued by
adult Ring-billed Gulls, but the Ross' Gull was not forced to give up its
catch. According to the "ranger" on duty at McNary on 28 November, juvenile
steelhead trout was the predominant species available that day.

It appears the displaced Ross' Gull on the Columbia River was utilizing a
food source and feeding technique similar to those employed in its usual
Arctic Ocean range.

Andy Stepniewski