Planktivorous auklet <i>Ptychoramphus aleuticus</i> responses to ocean climate, 2005: Unusual atmospheric blocking?

In spring‐summer 2005, anomalous atmospheric‐oceanographic coupling caused unprecedented reproductive failures and redistribution of a planktivorous marine bird in both central California (37°N) and southern British Columbia (50°N). At SE Farallon Island, CA, the birds abandoned the breeding colony en masse between 10–20 May, a unique behavioral response; for the first time in 35 years, reproductive success was zero. At Triangle Island, B.C., only 8% of the nesting pairs were successful, the worst year on record. Surveys of birds at sea revealed a peak in relative abundance south of Point Conception (34°N) in summer and fall, suggestive of emigration from the north. Prey (euphausiid crustacean) biomass in the Gulf of the Farallones was reduced, but remained high south of Point Conception. Change in predator and prey may be explained, in part, by unusual atmospheric blocking in the Gulf of Alaska in May, which caused the jet stream to shift southwards resulting in poor upwelling‐favorable winds and anomalously warm SST. This study demonstrates the deleterious consequences of this climate event for a top marine predator in the central‐northern California Current System.