The rise and fall of cliff-breeding seabirds in Sør-Varanger, NE Norway, 1970-2002

Abstract

Surveys of seabirds breeding along the coast of Sør-Varanger, NE Norway were carried out in 1989, 1996, 1999 and 2002 as a continuation of a monitoring study started in 1970. Until 1983, by which time 47 colonies were occupied, there had been a rapid increase in numbers of Black-legged Kittiwakes Rissa tridactyla and European Shags Phalacrocorax aristotelis breeding in the area while the Great Cormorant P. carbo population had first increased and then declined. Between 1983 and 2002, the Kittiwake and Shag populations declined by ca. 60% and 85% respectively while that of Cormorants first continued to decline and then recovered to levels recorded in the 1970s. The decline in Common Guillemot Uria aalge and Razorbill Alca torda numbers recorded since 1970 culminated in 1989 when no birds were seen in the region. Since then, one individual Common Guillemot was seen in 1999. In 2002 approximately 7500 pairs of Kittiwake, 770 pairs of Cormorant and 15 pairs of Shag bred in 23 colonies. Possible causes for the main population changes are briefly discussed.