Rhinoceros Auklet (Cerorhinca monocerata) Nestling Diet May Gauge Pacific Sand Lance (Ammodytes hexapterus) Recruitment

Abstract

We studied (1984–86) the diet of rhinoceros auklet (Cerorhinca monocerata) nestlings at three colonies on the British Columbia coast (Lucy islands, Pine Island, and Triangle Island). On the Lucy Islands, Pacific sand lance (Ammodytes hexapterus) dominated nestling food loads in all years. In 1985, 0+ sand lance dominated the nestling diet on all colonies. Concurrent measures of nestling growth rate, independent indexes of ocean production, and the proportion of sand lance in groundfish stomach samples were also highest in 1985. This suggests a linkage between ocean production, 0+ sand lance abundance, and events on seabird colonies over a broad geographic range. We emphasize the importance of sand lance to temperate seabirds and contrast British Columbia with areas where sand lance are commercially exploited. Rhinoceros auklet nestling diet, growth, and other data collected on colonies suggest that long-term monitoring on seabird colonies can contribute timely and inexpensive information on the recruitment of sand lance stocks in Canadian waters.