Seabird Abstracts

Differential responses of Common and Thick-billed Murres to

a crash in the Capelin stock in the Southern Barents Sea

Vader W, Barrett RT, Erikstad KE & Strann K-B (1990) Stud Avian Biol 14:175-180

Common Murres (Uria aalge) and Thick-billed Murres (U. lomvia) are common breeding birds in the Barents Sea, with complementary but overlapping distributions. Along the coast of North Norway, west of the North Cape, murre populations have been decreasing at least since 1965, probably as a result of breeding birds drowning in fishing nets. East of the North Cape and probably on Bear Island the populations have at least been stable until 1985. After 1985, numbers of breeding Common Murres decreased steeply in the entire area, by 70-85% in North Norway and ca. 90% on Bear Island, while populations of Thick-billed Murres decreased only slightly on the mainland and not at all on Bear Island. The numbers of murres wintering in the Barents Sea also decreased after 1986. It is thought that the differential decrease in numbers of breeding birds was a direct result of the sudden collapse of the Barents Sea capelin (Mallotus villosus) stock in 1985 and 1986, on which the Common Murres, but not the Thick-billed Murres, totally depended.


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