California Population 



Estimate 

 2,000 birds 



Offshore Sighting 

 =high 

 S =low 



Breeding Chronology 



Northern and Central California 



Clutdi- 1 (40) 



Incubation Period - 30 days 

 Nettling Period - 22 days 



(9,40,421 



em laying 



adults present 



* = 0'scowy of cft/c* in nnt. SM text. 



Note: Cllitomia chronology rft/e ,1 moaitiod from indirKt widfncf in Briritft Colombia 

 populitions. SffSffly. 1974: SMly. 197S. . 



Southern California 



Not Breeding 



Jan. | Feb. I Mar. | Apr. | May I June I July | Aug. I Sep. I Oct. I Nov. I Dc. 



coverage of the central and northern California 

 coasts was virtually complete. These two regions 

 were again censused in 1980, when we made 390 

 sightings of Marbled Murrelets, but our coverage 

 of the coastline in that year was less complete. 

 Both regions of high Marbled Murrelet concen- 

 tration are offshore of mature stands of coniferous 

 trees. This suggests that murrelets may require 

 these trees for nesting. After breeding, Marbled 

 Murrelets disperse along the coast of California. 

 They have been recorded as far south as Imperial 

 Beach, San Diego County (McCaskie 1980). 

 It is difficult to estimate the breeding pop- 

 ulation of Marbled Murrelets in California, but we 

 speculate that it is about 2,000 birds. This 

 estimate may be conservative since this small 

 alcid's breeding habits are poorly known. It is 

 difficult to see them at sea in other than perfect 

 conditions, and it is likely that other unobserved 

 murrelets were farther out to sea during our boat 

 surveys. Our observations of Marbled Murrelets 

 were made from a boat incidental to surveys of 

 other nesting seabirds. These surveys were not 

 designed to census Marbled Murrelets in the most 

 accurate fashion but we hope these results shed 

 some light on the species' nesting distribution in 

 the state. Further work on Marbled Murrelets is 

 certainly needed and our individual sight records 

 may be of future use to anyone attempting a 

 more complete survey of this species. All records 

 of our observations are included in the Colony 



Status Records and in our field notes (Appendix 

 A). 



HISTORICAL STATUS AND VULNERABILITY 



There is little information on the historical 

 status of Marbled Murrelets in California. Dis- 

 turbance to nesting Marbled Murrelets probably 

 has been and will continue to be primarily through 

 the destruction of nesting habitat. Populations of 

 Marbled Murrelets may have been reduced by the 

 destruction of virgin coastal forests, although no 

 data are available. The old growth stands of the 

 coast redwood alone have been reduced in area 

 from an estimated 809,000 hectares (2,000,000 

 acres) to 93,000 hectares (230,000 acres) (Veirs 

 pers. comm.). We suspect that Marbled Murrelets 

 were formerly more abundant than they are today. 



Marbled Murrelets are vulnerable to oil 

 contamination since they are often found on 

 waters very close to land. An oil spill along the 

 coastlines of Humboldt - Del Norte Counties or 

 San Mateo - Santa Cruz Counties could endanger 

 a murrelet population that is highly concentrated 

 during the summer months along those two 

 stretches of coastline. 



45 



