PERSISTENT SUMMER MORTALITIES OF COMMON MURRES ALONG THE OREGON CENTRAL COAST

Common Murres (Uria aalge) were found dead on Oregon central coast beaches every July-September from 1978 through 1990, but the magnitude of the mortality varied yearly. Many more hatching-year (HY) than after-hatching-year (AHY) murres usually were found dead. In some years, most HY murre mortalities happened shortly after HY murres had departed their natal colony, but, in other years, most mortalities occurred after HY murres had been at sea for some time and had grown substantially. These summer mortalities are not a recent phenomenon and, in spite of these mortalities, the total number of AHY murres censused at 15 Oregon colonies did not decrease between 1979 and 1988. Shooting, oiling, or entanglement in fishing gear appeared to cause few HY mortalities. The greatest number of beached HY murres occurred just before the 1982-1983 El Nino, and the fewest were found in 1983 during the El Nino.