Dive Behavior of the Double Crested (Phalacrocorax auritus) and the Pelagic (Phalacrocorax pelagicus) Cormorant at Cattle Pass, San Juan Island, WA

Abstract

The dive behavior of the Double Crested Cormorant (Phalacrocorax auritus) and the Pelagic Cormorant (Phalacrocorax pelagicus) was studied along Cattle Pass of San Juan Island, WA, USA. Dive durations and resting periods were measured for consecutive, sequential dives of each type of cormorant. Comparing the two species, mean dive time was greater for the Pelagic Cormorant. Both species exhibited dive to rest time ratios greater than one (>1) and therefore generate an oxygen debt that must be resupplied after completion of dive bouts. Tidal phase, including tidal height and current speed had an effect on when both species chose to forage. Further analysis of prey abundance and final resting locations in the Cattle Pass region are needed to understand more about the Double Crested and the Pelagic Cormorant’s dive behavior in the San Juan channel.