An Arctic breeding passerine takes advantage of winter phenotypic adjustments to migrate in the cold

Le Pogam, Audrey; O’Connor, Ryan; Love, Oliver; Petit, Magali; Régimbald, Lyette; Vézina, François

Flight of snow buntings during winter at Rimouski (Québec). Photo credit : Audrey Le Pogam
Flight of snow buntings during winter at Rimouski (Québec). Photo credit : Audrey Le Pogam

conditions by increasing their fat store and the mass of their flight muscles. These changes can increase their cold endurance through the production of more heat via shivering. However, birds also increase their fat stores and flight muscle size to provide fuel and  muscle force for long migratory flights. Given the similar phenotypic adjustments involved in cold acclimatization and migratory preparation, some birds that winter in cold temperate zones and then migrate to high latitudes to breed may benefit from winter phenotypic adjustments during later life-history stages, such as migration and arrival at cold breeding grounds.

To test whether a cold-acclimatized phenotype could be maintained, to provide an advantage for migration and arrival in the cold, we used the snow bunting (Plectrophenax nivalis), an Arctic breeding songbird known for its winter cold endurance. We monitored the phenotypic changes associated with cold acclimatization and pre-migration during the winter, spring migration and arrival/summer stages in a captive population. Specifically, we measured body composition (total, fat and lean body mass and pectoral muscle thickness), oxygen carrying capacity in the blood, maximum thermogenic capacity and endurance, cold tolerance and physiological maintenance cost

Our results show that although body mass, fat mass and physiological maintenance costs increase to support migration, the traits associated with cold acclimatization do not change in parallel since they are already high at the end of winter, thus providing an advantage for this species which may encounter a harsher climate during migration than at the peak of winter. This study also demonstrates the surprising ability of buntings to maintain an almost winter-like level of cold endurance into the summer when temperatures are higher than winter values, suggesting that buntings have evolved to maintain a winter phenotype into the summer months to cope with unpredictable weather events characteristic of the Arctic.

This study is the first direct demonstration that phenotypic traits associated with winter cold acclimatization can be transferred to the migratory phenotype and even maintained during the breeding season to provide an advantage for Arctic species.

Read the article in full here

Read the blog behind the research here

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