BIOLOGY AND CONSERVATION OF THE COMMON MURRE 5 



(e.g.. Ancient Murrelet Synthliboramphus antiquus) 

 raise their chicks almost entirely at sea, and "semi- 

 precociaT alcids (e.g., Cassin's Auklet Ptychoramphus 

 aleuticus) raise their chicks entirely at protected 

 breeding sites. Common murres often breed "shoulder- 

 to-shoulder" in large, dense colonies on the flat or 

 sloping surface of the ground (Figure 1.3) or on cliff 

 ledges (Figure 1.4). Most other alcids breed in large or 



Figure 1 .3. Breeding colony of common murres in the Upper Shubrick 

 Point study plot at the South Farallon Islands, California, May 1995 

 (Photo by M. W. Parker). 



Figure 1.4. Breeding colony of common murres at Puffin Rock near 

 Triangle Island, British Columbia, 1 6 July 1 985 (Photo by M. S. Rodway). 



small colonies where individual breeding sites are 

 present on cliff ledges, in rock crevices or other cavities, 

 or in excavated burrows. 



Reproductive Ecology 



Breeding Habitat 



The common murre breeds on the surface of the 

 ground in colonies on flat, sloping, or cliff habitats on 

 islands, or occasionally on the mainland, where breeding 

 sites are inaccessible to mammalian predators and have 

 low levels of human disturbance. Flat or gently sloping 

 habitats are used only where mammalian predation is 

 rare. For example, such habitats on small rock islands 

 are used extensively for breeding in California, Oregon, 

 and parts of Washington (Figure 1 .3; Boekelheide et al. 

 1990: Takekawa et al. 1990; Carter et al. 2001). 

 Mammalian predation or human disturbance often limit 

 breeding to cliff habitats in certain areas. For example, 

 in Alaska, where foxes have been introduced to islands 

 or are present naturally, cliff breeding predominates 

 (Bailey 1993). Cliff-face and cliff-top breeding occurs 

 widely and is well known at Tatoosh Island. Washington, 

 and Triangle Island. British Columbia (Figure 1.4; 

 Guiguet 1950: Campbell et al. 1990: Fairish 1995; 

 Carter et al. 2001 ). In some years, cliff-top subcolonies 

 at Tatoosh Island were subject to greater egg predation 

 by glaucous-winged gulls (Larus glaucescens) and 

 northwestern crows (Con'us caurinus) and greater 

 harassment by bald eagles (Haliaeerus leucocephalus) 

 and peregrine falcons (Falco peregrinus) than cliff-face 

 subcolonies (Parrish 1995. 19%). 



In California, Oregon, Washington, and British 

 Columbia, breeding habitat is very stable and does not 

 change substantially between years. However, erosion 

 of breeding habitats has been noted at certain colonies. 

 At the Double Point Rocks colony in central California, 

 a small natural arch used by small numbers of breeding 

 murres fell into the ocean between 1982 and 1985 

 (Takekawa et al. 1990). At the long-inactive Sea Lion 

 Rock colony in northern California, breeding by murres 

 has not been reported since the southern half of the rock 

 fell into the water sometime before the 1950s (Osbome 

 1972). Human degradation of breeding habitats has 

 occurred at several colonies of U. a. californica, 

 especially at the South Farallon Islands, Whaler Island. 

 Rockport Rocks, and Tillamook Rock (Carter et al. 

 2001). 



Seasonal and Daily Colony Attendance Patterns 



The annual cycle of colony attendance is divided 

 into three distinct periods, the breeding season, the at-sea 

 chick-rearing period, and the nonbreeding or winter 



