i found the following post to be of interest and hope you do too!
Hans Krauss Spokane, WA

Subj: Red-necked Grebes, Lesser B-b Gulls, Ravens
Date: 97-08-09 12:41:36 EDT
From: lopezba at atnet.at

Dear all, I shamelessly stole all this from The BWD Skimmer:

A study in Norway (by I. Byrkjedal, St. Eldoy, S. Grundetjern, M. K.
Loyning) has found that in early winter, most juvenile Red-necked Grebes
associated with Velvet Scoters while feeding, while virtually all adults fed
alone. It seems that the scoters, while catching their usual sea urchins,
crabs and small bivalves, dislodged a lot of polychaete worms from the
bottom of the bay, which the grebes fed on. The juveniles dive very close to
and at the same times as the scoters, and reappear close to where they went
down. In contrast, adult grebes mostly feed on small fish and have no
advantage from the scoter's feeding behaviour; they don't dive as frequently
as the juveniles and reappear far from where they descend. By March, only
low numbers of juveniles still fed together with scoters, the majority
having graduated to adult fish diets (which requires more skill, but has
higher nutritional value and requires less energy). No antagonistic
behaviour was observed. (Ibis 139)

Census of breeding Lesser Black-backed Gulls Larus fuscus are often done by
counting the nests in active colonies. According to a study by M.J.
O'Connell, J.C. Coulson, S. Raven and S. Joyce, this is not a reliable
method. They studied one colony with about 18,000 breeding pairs and found
that 27 % of the pairs that built nests failed to produce eggs; furthermore,
60 % of the pairs built multiple nests (up to four), but did not use more
than one nest. According to the study, only 61 % of the nests counted
actually represented breeding pairs. (Ibis 139)

M.L. Avery, M.A. Pavelka, D.L. Bergman, D.G. Decker, C.E. Knittle and G.M
Linz found that Raven could be trained not to predate on California Least
Tern eggs. They provided quail eggs treated with methiocarb, which made the
Raven feel sick, but did not kill or hurt them. The eggs were provided at
the tern nesting site before the terns laid, and at the edges of the colony
after laying had started. The Raven stopped predation at this site, but
continued at other sites. This measure had the positive side effect that the
resident Ravens not only left the tern eggs alone, but still protected the
site from other Ravens. Ravens had been shot in the past, which meant that
an other pair moved in within a few days and also had to be shot. (Colonial
Waterbirds 18)

Regards
Peter Hirsch
Vienna, Austria