Ohi Ltvtn^ Res(}itnv\ — Binls 



45 



of subadult and adult birds (Boekelheide and 

 Ainley 1989; Ainley and Boekelheide 1990). 

 Overall, numbers have remained stable or 

 increased in most areas in the region (e.g.. 

 Carter et al. 1992), whereas these birds now 

 occur at lower abundance than previously at the 

 South Farallon Islands (Ainley et al. 1994). 

 Numbers have increased in southern California, 

 but the birds ha\e suffered from gill-net and oil- 

 spill mortality as well as human disturbance at 

 colonies (H.R. Carter, unpublished data). 



Gulls, Terns, and Skimmers (Laridae and 

 Rynchopidae) 



The predominant nesting gull on the west 

 coast is the western gull (Lunis dccidcntalis). 

 Numbers have increased, especially in 

 California (Fig. 2). probably because of the 

 bird's use of human and fishing refuse and 

 reduced human disturbance. Numbers have 

 reached saturation at the world's largest colony 

 at the South Farallon Islands (Ainley et al. 

 1994); however, expansion is occuning at other 

 major colonies in central and southern 

 California (Carter et al. 1992). Glaucous- 

 winged gulls (L glaitcesceus) have remained 

 stable or increased in Puget Sound (Ll.W. 

 Wilson, unpublished data). 



California gulls (L. culiforulciis) have 

 recently expanded from interior colonies to nest 

 in San Francisco Bay (Fig. 2: Carter et al. 1992; 

 P. Woodin, San Francisco Bay Bird 

 Observatory, unpublished data). They face seri- 

 ous threats at inland colonies in interior 

 California because of water developments. At 

 the world's largest colony at Mono Lake, low 

 water levels have resulted in the formation of 

 land bridges to nesting islands, allowing access 

 by coyotes (Canis latnins) in certain years 

 (Jones and Stokes Associates 1993). Similar 

 problems exist at other northern California 

 colonies for many seabird and colonial water- 

 bird species (W.D. Shuford, Point Reyes Bird 

 Observatory, unpublished data). 



The status of California gulls at inland 

 colonies in Oregon and Washington is not well 

 known. Status and trends of inland colonies of 

 ring-billed gulls [L. deknvarensis) in California, 

 Oregon, and Washington are not known, 

 although problems related to low water levels 

 may occur at many colonies. Many thousands 

 have nested recently in northern California 

 (W.D. Shuford. unpublished data). Small num- 

 bers (< 500 breeding birds) also nest along the 

 Washington coast (Speich and Wahl 1989). 

 Small numbers (< 10 breeding birds) of 

 Heermann's gulls (L. heennuuni) nested in the 

 early I980's along the central California coast 

 but none are known to do so now. Franklin's 

 gulls (L. pipixcan) recently nested in small 

 numbers (< 100 breedins birds) at Lower 



California gull 



(1,000's) 



Western gull 



{10,000's) 



ND 



if 30- 



o 

 o 

 ^ 25- 



20- 



15- 



10- 



5- 



Glaucous-winged gull 

 (1,000's) 



ND 



12- 

 10- 



8- 



6 



4 



2- 



Black skimmer 



(100's) 



o ,_r 







75-80 89-91 79 88 78-82 91 

 CA OR WA 



Year 



7 

 6 

 5 

 4 

 3 

 2 

 1 



0— =^ 



5 ^ 



4 - 



3 — 



2 ■ — 



35- 

 30- 

 25- 



20 

 15 

 10 



5 



0- 



25- 

 20- 

 15- 



Klamath Lake, California, but their status in the 

 region is not known. 



Low thousands of Caspian. Forster's. least, 

 and elegant terns (Sterna caspia. S. forsteh. S. 

 uiitillaruiu, S. elegans) and black skimmers 

 (Rynchops iiiger) now occur in the region 

 through increases (especially along the southern 

 California coast) due to colony protection and 

 use of artificial nesting sites (Speich and Wahl 

 1989; Carter et al. 1992). Certain tern colonies 

 have been eliminated or shifted (especially in 

 San Francisco Bay) because of human distur- 

 bance and red fox (Vulpes viilpes) or other 

 mammalian predation (P. Woodin, unpublished 

 data). Overall, least tern colonies in California 

 appear somewhat stable because of extensive 

 management. They undoubtedly occur at lower 



ND 



Forster's tern 



(1,000's) 



— 



Least tern 



(100's) 



Elegant tern 



(lOO's) 







75-80 89-91 79 8 

 CA OR 



Year 



78-82 91 

 WA 



Fig. 2. Status and trends of breed- 

 ing populations of gulls, terns, and 

 skimmers. Small coastal popula- 

 tions of gulls (Heermann's and 

 ring-billed) and royal terns, as 

 well as large or small inland popu- 

 lations of gulls (ring-billed and 

 California), terns (black, gull- 

 billed, Caspian, and Forster's), and 

 black skimmers are not included. 

 ND — no data available: — no 

 coastal nesting. Sources: CA 

 (Huntetal. 1979: Sowls et al. 

 1980: Carter etal. 1992): OR 

 (Varoujean and Pitman 1979: R.W. 

 Lowe, unpublished data): and WA 

 (Speich and WM 1989: U.W. 

 Wilson, unpublished data). Also 

 see Carter et al. (in press) for dou- 

 ble-crested cormorant. 



