[Abstract not included]


The Farallon Islands are given as the type locality for the Ashy Petrel, Oceanodroma homochroa (Coues, 1864). Little of its biology has been studied, as information in the past has been limited to short period observations by visitors to off-shore islands along the California coast. Visitors of note were Cooper (1868), Bryant (1888), Blankinship (1892), Barlow (1894), Kaeding (1903), Emmerson (1904), Dawson (1911), Howell (1917 a and b), Loomis (1918), Thoresen (1960), and Bowman (1961).

The aim of this investigation is to provide a more detailed examination of the Ashy Petrel's breeding biology on the Farallon Islands, especially the growth of the chick, the pre-egg period, the post-egg period, and behavior.

Other common names used for this petrel have been Black Petrel, Lesser Black Petrel, Ashy Fork-tailed Petrel, and Coues Petrel (Grinnell and Miller, 1944). Synonyms are Cymochorea homochroa, Cymochorea monorhis homochroa, and Oceanodroma socorroensis.

Grinnell and Miller (1944) state that this petrel is fairly common along the coast in spring and summer, at least locally, and that the earliest and latest records were April 8 and November 16.

The Ashy Petrel is distributed off the California coast with known breeding stations (Grinnell and Miller, op. cit.) on the Farallon Islands, San Miguel Island and Santa Cruz Island. There are records for Monterey Bay, the sea near the Santa Barbara Islands, Point Reyes, Marin County, Smuggler's Cove, San Clemente Island, San Diego County, San Francisco Bay, and two young stray birds found in San Francisco (Orr, 1944).

This study was conducted on the Farallon Islands, specifically the southeastern part as shown on the map of the south Farallon Island, Figure 1, latitude 37° 42' North, longitude 123° 00' 1" West.

Birds were marked by using u.s. Fish and Wildlife Service aluminum bands and a combination of plastic color bands on the legs. The tips of the primaries and outer rectrices were also daubed with colored model airplane lacquers so that observations could be made without disturbing the birds. This allowed easy recognition of the nester through cracks in the rocks so that most of the time the bird was unaware of being observed. To check for eggs the bird was gently lifted with a stick as Davis (1957) had done with the storm Petrel.

This study was begun in the field on March 17 to April 2, 1964, and continued from June 2 to September 9, 1965 with some informational field material obtained by Richard Tenaza during July, 1966. It involved 816 hours of study of 269 individual nests, 108 chicks, and 184 eggs. The author built 40 rock nests, 12 of which were used by singers and unemployed birds but never had eggs laid in them; 8 had eggs laid in them but were never hatched; 18 nests produced chicks; 2 nests were never used. Of the 269 nests 45 were never used for any purpose. All observational work was done in the field.

LLU Discipline





Graduate School

First Advisor

Ernest S. Booth

Second Advisor

Earl W. Lathrop

Third Advisor

Leonard R. Bullas

Fourth Advisor

Edward D. Wagner

Fifth Advisor

Leonard Brand

Degree Name

Doctor of Philosophy (PhD)

Degree Level


Year Degree Awarded


Date (Title Page)




Library of Congress/MESH Subject Headings

Petrels -- California



Page Count

x; 265

Digital Format


Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.


Loma Linda University Electronic Theses and Dissertations

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Loma Linda University. Del E. Webb Memorial Library. University Archives

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