WINTER MOVEMENT ANALYSIS

RESULTS

Should I stay or should I go? There does not seem to be a unique answer to that question for wintering King Eiders, at least not based on the environmental variables that we measured. The most important variable that explained the variability in wintering strategies was the individual - different birds simply use different strategies. Some birds stay in one spot all winter, other birds move among several wintering sites. We found no support for the hypothesis that sea ice or food shortage would force birds to move away from certain sites.

So why are King Eiders so individually different? A potential explanation is that some birds may use favorable conditions (when days are long enough, and sea ice is decreasing) to explore alternative wintering sites. This might be beneficial in a future year when their preferred wintering site suddenly becomes unavailable.

The exploratory movements may be under frequency dependent selection, which would lead to the pattern that we currently observe: initially it may be advantageous for some birds to explore and obtain knowledge about alternative sites. However, if the majority of birds conducts exploratory movements, the individuals who remain at a site may have an advantage - they can conserve energy by not flying around, and in an emergency they can rely on the knowledge of other birds. So neither of the strategies will become dominant, and the population will always contain birds that move and birds that do not move in winter.

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