Seabirds in Southeastern Hawaiian Waters
WESTERN BIRDS Volume 30, Number 1, 1999 SEABIRDS IN SOUTHEASTERN HAWAIIAN WATERS LARRY B. SPEAR and DAVID G. AINLEY, H. T. Harvey & Associates,P.O. Box 1180, Alviso, California 95002 PETER PYLE, Point Reyes Bird Observatory,4990 Shoreline Highway, Stinson Beach, California 94970 Waters within 200 nautical miles (370 km) of North America and the Hawaiian Archipelago(the exclusiveeconomic zone) are consideredas withinNorth Americanboundaries by birdrecords committees (e.g., Erickson and Terrill 1996). Seabirdswithin 370 km of the southern Hawaiian Islands (hereafterreferred to as Hawaiian waters)were studiedintensively by the PacificOcean BiologicalSurvey Program (POBSP) during 15 monthsin 1964 and 1965 (King 1970). Theseresearchers replicated a tracklineeach month and providedconsiderable information on the seasonaloccurrence and distributionof seabirds in these waters. The data were primarily qualitative,however, because the POBSP surveyswere not basedon a strip of defined width nor were raw counts corrected for bird movement relative to that of the ship(see Analyses). As a result,estimation of density(birds per unit area) was not possible. From 1984 to 1991, using a more rigoroussurvey protocol, we re- surveyedseabirds in the southeasternpart of the region (Figure1). In this paper we providenew informationon the occurrence,distribution, effect of oceanographicfactors, and behaviorof seabirdsin southeasternHawai- ian waters, includingdensity estimatesof abundant species. We also document the occurrenceof six speciesunrecorded or unconfirmed in thesewaters, the ParasiticJaeger (Stercorarius parasiticus), South Polar Skua (Catharacta maccormicki), Tahiti Petrel (Pterodroma rostrata), Herald Petrel (P. heraldica), Stejneger's Petrel (P. Iongirostris), and Pycroft'sPetrel (P. pycrofti). STUDY AREA AND SURVEY PROTOCOL Our studywas a piggybackproject conducted aboard vessels studying the physicaloceanography of the easterntropical Pacific.
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