scheduled. 



These sonic booms may pose several potential 

 dangers to seabirds: 



1) High sonic boom pressures, particularly 

 those from launches, could physically damage 

 birds regardless of the time of year. 



2) Both surface nesting and burrow or crevice 

 nesting seabirds may desert eggs and young 

 or fail to initiate nesting because of sonic 

 booms. 



3) Death of eggs and chicks will probably occur 

 if sonic booms cause panic flights by adults. 

 This result would be similar to that already 

 discussed in the section "Human Distur- 

 bance." 



4) The nests of both burrow-nesting and 

 cliff-nesting seabirds could be damaged or 

 destroyed. An underground nuclear blast in 

 Colorado reduced local raptor reproduction 

 by 20 percent when cliffs crumbled and 

 crushed eggs in two of nine nests (Stahlecker 

 and Alldredge 1976). Sound pressures from 

 the Space Shuttle sonic booms may produce 

 a similar effect. Sonic booms in Arizona 

 reportedly have caused geological damage 

 (Graham 1969). Subterranean - nesting 

 species would be particularly vulnerable to 

 the shifting of rocks and soils. 



METHODS 



Information compiled in this catalog comes 

 from four primary sources. The U.S. Fish and 

 Wildlife Service (this study) conducted surveys of 

 seabirds in 1979 and 1980 along the California 

 coast from Point Conception to the Oregon 

 border. An initial survey of this part of the coast 

 was conducted in 1969 and 1970 by Osborne 

 and Reynolds (1971), and their data still provide 

 the best population estimates for some species at 

 some sites. Data for the Channel Islands and the 

 coast south of Point Conception come primarily 

 from another BLM-sponsored oil lease study 

 conducted from 1974 to 1977 by Hunt et al. 

 (1979) and the California Department of Fish and 

 Game. Information for the Farallon Islands has 

 been collected over the past ten years by staff 

 members of the Point Reyes Bird Observatory. 

 Other sources are listed in the references section 

 and in colony tables. All persons known to have 



gathered recent data compiled in this catalog are 

 listed on the title page under "Contributors". 



Inherent in any collection of data from 

 different sources is variability in methods. No 

 attempt has been made to enumerate all techniques 

 used to collect data presented in this catalog. 

 Instead we refer readers to the appropriate 

 references from which we obtained population 

 estimates listed in this catalog (After each line of 

 data in the Maps and Tables section, we reference 

 the source from which we obtained the inform- 

 ation). A detailed account of the techniques we 

 used during our 19 79 and 1980 surveys is presented 

 below. 



We conducted seabird surveys from Point 

 Conception to the Oregon border from mid-May 

 to mid-August, 1979, and from mid-May to late 

 August, 1980. Adequate coverage of such a long 

 stretch of coastline required two teams of two 

 observers each with a vehicle, an inflatable 

 boat, and two outboard engines. In 1980, a fifth 

 observer was added to the team. Surveys were 

 concentrated during the peak of the nesting 

 season, from late May to late July. Surveys of 

 surface-nesting seabirds completed earlier in 

 May when seabirds began nesting were repeated 

 later in the season to determine the maximum 

 breeding population. We concentrated our 1979 

 surveys on conspicuous, diurnal, surface-nesting 

 species such as Brandt's Cormorants, Pelagic 

 Cormorants, Western Gulls, Common Murres, and 

 Pigeon Guillemots. In 1980-, we divided our time 

 equally between censusing diurnal surface-nesting 

 seabirds and censusing nocturnal burrowing 

 species such as storm-petrels and Rhinocerps 

 Auklets. 



All sections of coastline with likely seabird 

 nesting habitat were surveyed by boat one or 

 more times. Least Terns nesting in bays and on 

 beaches were not counted, since their populations 

 are surveyed annually by the California Depart- 

 ment of Fish and Game. We did not attempt to 

 census Snowy Plovers (Charadrius alexandrinus), 

 Clapper Rails (Rallus longirostris), American 

 Avocets (Recurvirostra americana), Black-necked 

 Stilts (Himantopus mexicanus), or some of the 

 other species mentioned by Varoujean (1979) in 

 his catalog of seabird colonies of the Pacific 

 States, which was completed from available 

 literature before our surveys were made. 



Counts were made from inflatable boats 

 using 7X binoculars or the unaided eye. We 

 found that binoculars with a wide-angle field of 

 view were far superior to normal binoculars when 

 counting from boats. Whenever possible, direct 



