Warm Ocean Hard on Cassin's Auklets
Warmer than usual water off the southern British Columbia coast during the 1990s ultimately led to a crash in BC's Cassin's auklet population.
On Triangle Island, near Vancouver Island's north coast, annual adult survival was typically 71 percent, with 60 percent of burrows occupied.
The heated California current in this region produces a minimal supply of zooplankton, the birds' food source.
At Frederick Island, breeding Cassin's auklets were more successful, with normal adult survival rates of 80 percent and the birds using 85 percent of the burrows available for breeding. Here, in the Queen Charlotte archipelago, the Alaska current maintains a high level of zooplankton productivity.
But breeding populations on both islands dropped by 20 to 30 percent in 1998, during El Niño. For all Cassin's auklets, southern wintering grounds in the California current failed to produce enough food that year. Massive declines in zooplankton occurred in conjunction with rising marine temperatures. The bird populations began recovering in 1999 when the ocean cooled.
Douglas F. Bertram, Anne Harfenist and Barry D. Smith. 2005. Ocean climate and El Niño impacts on survival of Cassin's Auklets from upwelling and downwelling domains of British Columbia. Canadian Journal of Fisheries and Aquatic Sciences. 62: 2841-2853.