“Energetic physiology mediates individual optimization of breeding phenology in a migratory Arctic seabird”

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Holly L. Hennin, Joël Bêty, Pierre Legagneux, H. Grant Gilchrist, Tony D. Williams, and Oliver P. Love

A female common eider (Somateria mollissima) at East Bay Island takes a short break from incubation.
(Credit: H. Grant Gilchrist)

Fattening quickly while saving energy benefits earlier breeding

Organisms exhibit an impressive diversity of breeding strategies from parthenogenesis to live birth. Regardless of the method, all organisms need enough energy to reproduce successfully. Migratory species breeding in highly seasonal environments are faced with highly restrictive time constraints and often limited access to the resources they need to breed. Over 20 years ago, Rowe and colleagues (Am. Nat. 143, p. 698) predicted that individuals better able to gain in condition should be able to reproduce earlier and gain the highest reproductive success. However, until now, no study has been able to test in the wild whether fattening rate impacts reproductive timing, a trait highly critical to offspring survival.

Arctic-breeding female common eider.
(Credit: H. Grant Gilchrist)

To examine these questions Holly Hennin and colleagues from the University of Windsor, Environment and Climate Change Canada, Université du Québec à Rimouski, and Simon Fraser University used an 8-year data set (2006-2013) from Arctic-breeding common eiders (Somateria mollissima) nesting on a small island in the Eastern Canadian Arctic. The team was able to capture hundreds of pre-breeding females and collect blood samples to assess their current level of energy demand and fattening rates. The researchers can then track individuals in the colony to assess whether variation in these arrival physiological traits ultimately impact the timing of breeding. The team confirmed Rowe et al.’s (1994) key model predictions: Females able to fatten quickly while maintaining low energy demands had the shortest delays from arrival to laying, and most critically, laid the earliest. In addition to testing this important model, the research also provides insight into the energetic mechanisms that enable individuals to fine-tune the timing of breeding within temporally-constrained, stochastic environments. Since these mechanisms likely precede gonadal activation, they may play central regulatory roles in the timing of reproduction across vertebrates. Read the Article