Marine Ornithology 32: 159–165 (2004) POPULATION STATUS, FOODS AND FORAGING OF LAYSAN ALBATROSSES PHOEBASTRIA IMMUTABILIS NESTING

During the 1983/84 winter breeding season, Laysan Albatrosses Phoebastria immutabilis bred in the eastern Pacific for the first time in recorded history, on Guadalupe Island, Mexico. By 1991/92, the last reported census, the population had grown to 45 pairs. We conducted censuses during 1999/2000 and 2000/01 and found that, in addition to nesting at the only previously known colony (on the main island), albatrosses were breeding at another site on the main island and on two offshore islets. We estimated the entire population to be a minimum of 119 and 193 pairs for each of the two seasons respectively. Although the colonies on the main island are threatened by predation pressure from introduced mammals, the offshore islets remain predator-free. During June 2000, we also collected 27 chick regurgitation pellets (comprised only of indigestible hard parts) for analysis of diet. The pellets included beaks from a minimum of 964 individual cephalopods representing a minimum of 12 families and 22 species. The most common species were squids: Histioteuthis hoylei (20.4 % of identified beaks), Taonius borealis (13.8%), Gonatus pyros (11.2%), and Galiteuthis? sp. A (11.0%). A previous study from colonies in Hawaii identified ommastrephid squids as the most important prey, but we did not find any in our sample. The reason(s) for this discrepancy are not clear. It has been suggested that Laysan Albatrosses catch squid at night, taking them alive when they migrate to the surface. Most of th