PATTERNS OF MOVEMENT OF DARK-RUMPED PETRELS AND NEWELL SHEARWATERS ONKAUAI

We used ornithological radar and night-vision scopes to study movement patterns of Dark-rumped Petrels (Pterodroma phaeopygia sandwichensis) and Newell's Shearwaters (Puffinus auricularis newelli) on the island of Kauai, Hawaii, from 1992 to 1994. Movement rates on radar (targets /hr) for both species peaked for similar to 2 hr around sunset and sun rise and were low in the middle of the night. Dark-rumped Petrels gene rally moved during crepuscular periods, whereas Newell's Shearwaters w ere strongly nocturnal. Movement rates were much higher in fall 1993 t han in fall 1999, probably because of effects of Hurricane Iniki in 19 92, and were higher in summer than in fall, probably because of the pr esence of nonbreeding birds in summer. Movement rates increased throug h time in summer, probably because numbers of nonbreeding birds visiti ng colonies increased through time, but declined through time in fall because fewer adults returned to the colony as fledging progressed. Ef fects of the moon on movement rates appeared to be small. Movement rat es varied geographically, generally being much higher on eastern and n orthern Kauai than on southern Kauai. Movements were predominantly inl and in the evening, predominantly seaward in the morning, and both dir ections in the middle of the night. Birds flew between 8 and 800 m abo ve ground level (agl) and averaged 142 m agl for all procellariid spec ies combined. There was no relationship between elevation of a site an d flight altitude of birds at that site. Flight altitudes at a site ge nerally were highest during the evening peak of movement and lowest du ring the morning peak in summer but were not different among three per iods of the night in fall. Dark-rumped Petrels flew at significantly h igher altitudes than did Newell's Shearwaters in fall 1993 and summer 1994 but not in summer 1993.