Does spring ice cover influence nest initiation date and clutch size in common eiders?

Abstract

Understanding how environmental factors aVect ecological parameters is important to understanding and predicting impacts of environmental change. Given evidence and anticipated impacts of climate variability, this is especially true with respect to sea ice and its role in animal life history in northern regions. We examined relationships between the extent of consolidated spring ice cover (pack and landfast), nest initiation and clutch size in common eiders (Somateria mollissima) in northern Labrador, a sub-Arctic region on the east coast of Canada. Our initial prediction was that eiders would delay nesting and have smaller clutches in years with more extensive spring ice cover. Between 1998 and 2003, we surveyed coastal islands for breeding eiders and collected information on nest age and clutch size. For those years, we estimated ice cover based on Radarsat-1 images supplied by the Canadian Ice Service during the spring period (approximately June 7-12). We found that spring ice cover was a signiWcant positive predictor of nest initiation date, and the regression equation indicated that if the average extent of ice cover around nesting islands increased by 18 ha, average nesting date was delayed by approximately 1 day. Nest initiation date was a signiWcant negative predictor of clutch size, and the regression equation indicated that a 20 day delay in nesting reduced average clutch size by approximately 1 egg. However, ice cover itself was not a signiWcant predictor of clutch size. Our Wndings suggest that eiders breed when ice is present, but ice extent may negatively inXuence aspects of their breeding ecology.

A natural antipredation experiment: predator control and reduced sea ice increases colony size in a long‐lived duck

“…For eiders and other ground nesting species, these changes are likely to have substantial effects as ice breakup around the breeding colonies prohibits predation from Arctic foxes (Mehlum ; Svendsen et al. ; Chaulk and Mahoney ). In years with little ice and/or early ice break‐up in the spring, the eiders also have earlier access to the benthic invertebrates that they rely upon for building up their energy reserves prior to breeding.…”

“…The birds preferably breed on islets to avoid terrestrial nest predators and they are unwilling to start breeding until the sea ice around the islets is melted (Mehlum ; Svendsen et al. ; Chaulk and Mahoney ). Eider ducks in the Arctic suffer from high levels of nest predation from a range of species (Ahlén and Andersson ; Mehlum ; Noel et al.…”

The early birds and the rest: do first nesters represent the entire colony?

“…There is general agreement that spring arrival of common eider is influenced by climate variation, both in higherArctic conditions where ice covers the nest sites until spring and in sub-Arctic or temperate locations where spring ice cover is absent and low-pressure winters delay first nest dates Jónsson et al 2009;D'Alba et al 2010;Love et al 2010;Chaulk and Mahoney 2012;Mehlum 2012). Thus, the importance of such parameters cannot be understated for study of this species, which is often too numerous and/or dispersed to count annually.…”

Common Eider and large gull and nesting associations in coastal Labrador

“…It is likely that eiders and gulls are drawn to similar nesting islands with certain environmental characteristics such as being offshore to avoid mammalian predators (Robertson 1995;Wyman et al 2014). In Labrador, eiders show a strong preference for islands that do not trap ice in spring, and so would not be connected to mainland areas and accessible to mammalian predators (Chaulk et al 2007;Chaulk and Mahoney 2012). Presumably, gulls would also be attracted to nest on these islands for the same protection from mammals.…”