Predation on American Common Eiders in Eastern Nova Scotia, Canada

Molly D. Tomlik^1,2, G. Randy Milton^1,3,4, Glen J. Parsons^1,3, and Mark L. Mallory^1,*

¹Biology Department, Acadia University, 33 Westwood Avenue, Wolfville, NS B4P 2R6, Canada. ²Current address - Canadian Wildlife Service, 17 Waterfowl Lane, Sackville, NB E4L 1G6, Canada. ³Nova Scotia Department of Natural Resources, 136 Exhibition Street, Kentville, NS B4N 4E5, Canada. ⁴Gulbali Institute for Agriculture, Water and Environment, Charles Sturt University, Wagga Wagga, New South Wales 2678, Australia. *Corresponding author.

Northeastern Naturalist, Volume 33, Issue 3 (2026): 395–412

First published early online: 20 September 2026

Abstract
Somateria mollissima dresseri (American Common Eider) numbers are declining in parts of their historic breeding range in eastern North America. We conducted nesting surveys on 16 islands in 2013 to investigate eider breeding phenology and breeding effort, and whether predation pressure on eiders nesting in the Eastern Shore Islands Wildlife Management Area could be contributing to observed declines in eider numbers in Nova Scotia, Canada. We found 827 nests on islands with and without mammalian or avian predators. Hens nesting on islands with some predators, initiated nests a few days earlier and had slightly larger clutches than hens on islands with fewer types of predators, but overall, types of predators on islands did not result in significantly different eider nest success. We observed 25 eider carcasses in total on 11 of the 16 islands and thereby estimated that predators killed a minimum of 3% of the nesting female eiders during the breeding season. Given the importance of hen survival to long-lived bird species population growth, monitoring predator populations on islands supporting colonial nesting birds is warranted.

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