BIOLOGY AND CONSERVATION OF THE COMMON MURRE 1 5 



Colony formations also can be facilitated with the 

 use of social attraction techniques. In 1996-2000. murre 

 decoys and broadcasted murre vocalizations were 

 successfully used as social attraction methods at Devil's 

 Slide Rock, California, to recolonize this previously- 

 extirpated "colony complex" where murres no longer 

 bred within 35^tt) km of this location (Graham 1996; 

 Parker et al. 1997, 1998, 1999; Helmuth 1999; Parker 

 1999; Carter etal. 2001). 



Several natural and anthropogenic factors can affect 

 breeding conditions at an active colony and may 

 contribute to colony formations by providing impetus 

 for adults or subadults to attend other breeding habitats. 

 Colony sites suffering from chronic impacts or persistent 

 low numbers of attending birds may be abandoned. If 

 such abandonment has resulted from anthropogenic 

 factors, these colonies have been referred to as 

 "extirpated," even though suitable breeding substrates 

 remain. Colony extirpation has occurred for many 

 decades at certain locations in California because of 

 human disturbance, breeding habitat changes, and 

 egging (Carter et al. 2001). However, it was not 

 determined whether any surviving murres moved to 

 other colonies or no longer bred. More recently, 

 extirpation or abandonment of several murre colonies 

 has occurred along the southern Washington coast, 

 evidently because of a combination of natural and 

 anthropogenic factors (Wilson 1991 ; Carter et al. 2001 ). 

 Corresponding changes in numbers on adjacent colonies 

 also has been noted in Washington and California, 

 suggesting that murres will move, either temporarily or 

 permanently, to adjacent colonies under certain 

 circumstances (Carter et al. 2001). However, such 

 movements and subsequent breeding have not been 

 verified with banded birds. 



Irregular attendance at potential breeding habitats 

 (and, at times, nonbreeding habitats) also has been 

 recorded at many locations from California to British 

 Columbia (Carter et al. 2001). Such attendance was 

 considered to be sporadic (i.e., attendance interspersed 

 with periods of absence) during the breeding season 

 when regular attendance typically occurs at colonies 

 (see above; McChesney et al. 1998). At potential 

 breeding habitats, such behavior may reflect attendance 

 (with or without attempted breeding) at a colony site in 

 the process of being abandoned, extirpated, colonized, 

 or recolonized. In Washington, irregular attendance at 

 several colony sites and nonbreeding habitats may 

 reflect attempts to change breeding sites, or to continue 

 breeding at low levels under conditions of population 

 decline (Carter etal. 2001). 



Predators 



Common murres usually breed in colonies on 

 islands or mainland cliffs that are free of mammalian 

 predators. On flat areas, slopes, or cliffs, murres breed in 

 dense concentrations which reduce predation of eggs 

 and chicks by avian predators. Other ecological 

 adaptations which can reduce predation include large 

 body size, constant attendance of breeding sites, and 

 active defense of breeding sites against predators. 

 However, surface breeding makes murres susceptible to 

 predation of eggs and chicks by various avian predators. 

 In California, Oregon, Washington, and British 

 Columbia, chief predators of eggs and chicks include 

 western gulls, glaucous-winged gulls, common ravens 

 (Corvus corax), American crows (Corvus 

 brachyrhynchos), northwestern crows, and occasionally 

 brown pelicans (Pelecanus occidentalis; Boekelheide 

 et al. 1990; Rodway 1990; Spear 1993; Parrish 1995; 

 Parker etal. 1997, 1 998; Thayer etal. 1999; R.W.Lowe, 

 unpublished data). 



In Alaska and Newfoundland, Arctic foxes (Alopex 

 lagopus) and red foxes (Vulpes vulpes) prey on murres 

 at some colonies, which can result in colony 

 abandonment, low reproductive success, delayed 

 breeding, or reduced breeding attempts (Bailey 1993; 

 Birkhead and Nettleship 1995). In California, Oregon, 

 Washington, and British Columbia, adult and subadult 

 murres are taken alive at or near colonies by peregrine 

 falcons, bald eagles, other raptors (e.g., red-tailed hawk 

 [Buleo jamaicensis]), large gulls, and occasionally 

 marine mammals (Bayer 1986; Paine et al. 1990; 

 Rodway 1990; Garcelon 1994; Harding 1994; Parrish 

 1995, 1996; R. W. Lowe, unpublished data; M. W Parker, 

 unpublished data). However, some dead murres 

 discovered in raptor nest remains may have been 

 scavenged at sea or from shorelines. At some colonies, 

 disturbances by eagles chasing or capturing murres has 

 severely impacted breeding murres in Washington and 

 Oregon in recent years (Speich et al. 1987; Parrish 1995; 

 Warheit 1997; Carter et al. 2001). In 1999, as much as 

 half of the Oregon murre population may have been 

 affected to varying degrees by eagle disturbance, 

 compared to little if any impact before 1994 (R. W. 

 Lowe, unpublished data). It is unclear to what extent 

 such disturbances occurred at these murre colonies in 

 historical times when both eagle and murre numbers 

 probably were higher. Current disturbances may reflect 

 recent use by murres of breeding habitats susceptible to 

 such disturbances at certain colonies (e.g., cliff-top 

 habitats at Tatoosh Island) and recent expansion of eagle 

 populations (Parrish 1995; Carter et al. 2001). 



