Seabird Abstracts

Decline of the Common Murre in central California, 1980-1986

Takekawa JE, Carter HR & Harvey TE (1990) Stud Avian Biol 14:149-163

Aerial surveys of 13 Common Murre (Uria aalge) colonies were conducted in California in 1985 and 1986. Breeding population estimates for eight colonies in central California and five colonies in northern California were compared with estimates determined in 1980-1982. The central California population declined 52.6% within 4-6 years, from 229,080 in 1980-1982 to 108,530 in 1986. The northern California population remained relatively unchanged during the same period; combined totals at four colonies declined 5.4% from 118,080 in 1979-1982 to 111,730 in 1986. Population decline in central California was caused by high mortality from an intensive nearshore gill-net fishery, compounded by that from oil spills and a severe El Nino-Southern Oscillation event in 1982-1983. Individual colonies declined 45.8-100% and the most severe declines occurred at colonies located nearest to areas of highest gill-net fishing mortality.


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