Late Ice-off Negatively Influences Breeding in Common Loons (Gavia immer)

Kristin Bianchini^1,2, Robert Alvo³, Douglas C. Tozer^1,*, and Mark L. Mallory²

¹Long Point Waterfowl and Wetlands Research Program, Birds Canada, PO Box 160 (Courier: 115 Front Road), Port Rowan, ON N0E 1M0, Canada. ²Biology Department, Acadia University, Wolfville, NS B4P 2R6, Canada. ³45 Holland Avenue, Unit 210, Ottawa, ON K1Y 4S3, Canada. *Corresponding author.

Northeastern Naturalist, Volume 28, Issue 1 (2021): 65–76

Abstract
Productivity of Gavia immer (Common Loon) has declined in Ontario and across southern Canada. Variations in the timing of lake ice-off have the potential to negatively influence productivity of Common Loons, but there is conflicting evidence as to how ice-off dates affect this species’ reproductive success. Our study investigated the association between annual ice-off timing in southern Ontario and the presence and reproductive success of Common Loons surveyed at 69 small lakes in 16 years over a 38-year span (1982–2019). We found negative relationships between residual ice-off date and the presence of Common Loon pairs, the proportion of Common Loon pairs attempting to breed, and the number of large young per pair per year, suggesting that there were fewer pairs, breeding attempts per pair, and large young per pair in years with later ice-off dates. Our results show that ice-off date is an important factor affecting reproduction in Common Loons, and that ice-off dates can be used to help predict annual variations in productivity of Common Loons.

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