STABLE ISOTOPE ANALYSIS

OBJECTIVES

Stable isotope analysis makes use of naturally occurring isotopes of certain elements. The ratio of these isotopes differs between geographic areas and environments. For example, marine environments typically show different isotope ratios than terrestrial environments. Animals that forage in a certain area ingest material with an area- specific isotopic signature. If this energy is used for growth, i.e. for feather growth in birds, the feathers will carry the isotopic signature of the area where the bird was feeding when it grew the feathers. By analysing the stable isotope ratios in certain tissues it is possible to know where a bird was when these tissues were synthesized.

King Eiders require some body reserves to breed successfully, and these body reserves may be accumulated prior to or during spring migration. Using stable isotopes in feathers and claws we can determine where a King Eider spent the previous winter by catching the bird on the breeding grounds. We aim to study carryover effects in King Eiders by relating the breeding success of females to their wintering location in the previous winter.

Many birds in the arctic have only very little time for breeding, as the arctic summer is very short. Especially large birds may therefore arrive with energy reserves that will enable them to lay eggs from stored nutrients. For King Eiders it is not known to what extent they rely on food available on the tundra during egg formation. We address this question by analysing the stable isotope ratios in egg tissues and food items of King Eiders.

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