Out Living Rt'sourcfs — Biril.s 



47 



killed in gill nets in central California between 

 1979 and 19S7. before heavy fishing restrictions 

 were imposed in 1987 to stop mortality 

 (Takekawa et al. 1990). Additional moitalit\ 

 (10.000+ murres) occurred during the 1984 

 Puerto Rican and 1986 Ape.x Houston oil spills 

 (Ford et al. 1987; Page et al. 1990). At the South 

 Farallon Islands, reproductive success was 

 almost nil during intense El Niiio events in 198.^ 

 and 1992 (Ainley and Boekelheide 1990: W.J. 

 Sydeman. unpublished data). Because of these 

 and other factors, the central California popula- 

 tion declined by over biWc from 1982 to 1989 

 and has not recovered (Fig. 4; Takekawa et al. 

 1990; Carter et al. 1992;" Ainley et al. 1994; 

 H.R. Carter, unpublished data). 



In Washington, mune numbers crashed dur- 

 ing the 1982-83 El Niiio (Wilson 1991), 

 although there was heavy mortality from gill 

 nets at this time; mortality from gill nets still 

 continues in Puget Sound. In addition, certain 

 colonies have been disturbed by low-tlying air- 

 craft, especially near military bases. Numbers 

 of breeding murres in Washington are lower 

 than indicated in Figs. 3 and 4 because many 

 birds counted in colonies in recent years (and 

 used to derive estimates) do not appear to be 

 breeding (U.W. Wilson, unpublished data). 

 Significant inortality occurred during the 1984 

 Arco Anchorage. 1988 Nestucca. and 1991 

 Tenyo Mciru oil spills. In the Nestucca spill 

 alone, about 30,000 murres were estimated to 

 have died (Ford et al. 1991). The Washington 

 population of murres has been almost extirpat- 

 ed over the last decade and has not recovered. 



In contrast, murre populations in Oregon and 

 northern California have been stable or increas- 

 ing to date, despite human disturbance at sever- 

 al colonies (Takekawa et al. 1990; R.W. Lowe, 

 unpublished data) and some losses of Oregon 

 birds from oil spills and the use of gill nets in 

 Washington. In addition, these areas were 

 known to experience lower productivity through 

 colony abandonment during intense El Nino 

 conditions in 1993 (Fig. 4; H.R. Carter, unpub- 

 lished data; J.E. Takekawa and R.W. Lowe, 

 unpublished data). Thus, it appears clear that 

 decline and lack of recovery of populations in 

 central California and Washington have resulted 

 primarily from human causes, especially gill 

 nets and oil spills. 



Marbled murrelets probably have declined 

 substantially throughout the region largely 

 because of the direct loss of most (90% -95*^ ) of 

 their old-growth forest nesting habitat to large- 

 scale logging since the mid-1800"s (Carter and 

 Morrison 1992; FEMAT 1994). About 10.000- 

 20.000 birds remain. In addition, hundreds of 

 munelets have been killed in gill nets and oil 

 spills in central California. Puget Sound, and off 

 the Olympic Peninsula (Carter and Momson 



1992; H.R. Carter, unpublished data), Murrelets 

 appear to have vei-y low reproductive rates 

 (based on nests examined and at-sea counts of 

 juveniles), probably because of high avian nest 

 prcdation in fragmented forests and possibly 

 lower breeding success during intense El Nifio 

 events. This species was listed as threatened in 

 California, Oregon, and Washington in 1992, 

 and is being considered carefully with regard to 

 the future of old-growth forests and the timber 

 industry in this region. Small populations in 

 California, Oregon. and southwestern 

 Washington are isolated and susceptible to 

 extinction from various potential disturbances 

 in the future. 



Washington 



W(10,000's) 

 .-.-■■■I 



Oregon 



(100,000's) 





ND ND ND ND ND ND ND ND 



25 

 20 

 15 



Central California 

 (10,000's) 



ND 



ND 



ND ND ND 



ND 



ND ND 



79 80 81 82 83 84 85 



87 88 



90 91 92 93 



Year 



The Xantus" murrelet (Synthliboramphus 

 Inpoleucus) persists in very low numbers 

 (2.000-5.000 breeding birds) only in southern 

 California. Numbers breeding at the largest 

 colony at Santa Barbara Island probably have 

 declined between the mid-1970"s and 1991 

 (Fig. 3; Carter et al. 1992). The decline may 

 have occuiTcd because of many factors, includ- 

 ing census differences. Poor reproduction, how- 

 ever, has occurred because of high levels of 

 avian and mammalian predation and has proba- 

 bly led to this decline. Other smaller colonies 

 may disappear because of mortality from oil 

 spills from offshore platforms in Santa Barbara 

 Channel and oil tanker traffic into Los Angeles 



Fig. 4. Status and trends of 

 breeding populations of common 

 murres in Washington. Oregon, 

 and central California. ND — no 

 data available. Sources: WA 

 (Wilson 1991; U,W. Wilson, 

 unpublished data); OR (Varoujean 

 and Pilman 1979; R.W. Lowe, 

 unpublished data); and Central 

 CA (Takekawa et al. 1990; Carter 

 etal. 1992; H.R. Carter and J.E. 

 Takekawa, unpublished data). 



