Does Kleptoparasitism by Glaucous-winged Gulls limit the reproductive success of Tufted Puffins?

Auk, The, Oct 2001 by St Clair, Colleen Cassady, St Clair, Robert C, Williams, Tony D

There are a couple of potential explanations for the accessibility effect, which was more pronounced in 1995. One possibility is that burrows at higher elevations with shallow slopes are in poorer condition, due to thinner ceilings caused by the shallower slope, greater human visitation over many years, and proximity of nesting gulls that pull out and trample the vegetation. Although better burrow condition was related to higher chick survival in 1996 (chi^sup 2^ = 5.8, df = 2, P = 0.055), the two were not related in 1995 (chi^sup 2^ = 0.12, df = 2, P = 0.94) and elevation did not differ among three burrow condition categories in either year (F 0.42). A second possibility is that burrow location on the nesting slope correlates with parental quality. Some evidence for that suggestion comes from the fact that lower elevations were accompanied by higher burrow densities (r^sup 2^ = 0.16, df = 1 and 40, P = 0.006) which generally correlate with earlier breeding and higher fledging success (Harris 1984).

It seems likely that fledging success is primarily dictated by causes other than slope attributes or gull activity and those will require further study. Because puffins likely evolved under conditions of unpredictable prey (Kitaysky 1996), annual differences in food availability (Vermeer et al. 1979) more likely cause seasonal differences in reproductive success. Greater effects of kleptoparasitism might be realized if it increased in frequency (e.g. Nettleship 1972) or if foraging costs for puffins were to rise (e.g. Gorman et al. 1998) due, for example, to low prey availability. Thus, kleptoparasitism may slightly exacerbate poor food years for puffins (Harris 1984, Furness 1987), but gulls do not seem to cause, or substantially contribute to, reproductive failures that afflict puffins at that site.

ACKNOWLEDGMENTS

Financial and logistical support for this project were provided by Research Network Program Grants through the Wildlife Ecology Chair (jointly supported by Simon Fraser University, the Canadian Wildlife Service, and the Natural Science and Engineering Research Council of Canada), by an Izaak Walton Killam Memorial Postdoctoral Fellowship to C.C.S. and an NSERC operating grant to T.D.W. We thank G. Gilchrist and I. Jones for proposing a study on kleptoparasitism and securing the initial funding for it. D. Bertram, L. Cowan, J. Kendall, A. King, S. Romain, J. Salatas, R. Torres, A. Watt, and M. Wiley provided invaluable assistance and wonderful company in the field, and D. Bertram, S. Carroll, E Cooke, E. Danchin, J. Dunn, S. Hannon, and D. Oro provided helpful comments on the subsequent analysis and manuscript.

LITERATURE CITED

ARNASON, E., AND P. R. GRANT. 1978. The significance of kleptoparasitism during the breeding season in a colony of Arctic Skuas Stercorarius parasiticus in Iceland. Ibis 120:38-53.

BARNARD, C. J., AND D. B. A. THOMPSON. 1985. Kleptoparasitism: Host and prey selection by gulls. Pages 217-254 in Gulls and Plovers: The Ecology and Behavior of Mixed-species Feeding Groups (C. J. Barnard and D. B. A. Thompson, Eds.). Croom Helm, London.