Abstract
Migratory behavior, routes and zones used during the non-breeding season are assumed to have been selected to maximize fitness, and can lead to genetic differentiation. Yet, here we show that migration strategies differ markedly between and within two genetically similar populations of wandering albatross Diomedea exulans from the Crozet and Kerguelen archipelagos in the Indian Ocean. Wandering albatrosses usually breed biennially if successful, and during the sabbatical year, all birds from Kerguelen migrate to the Pacific Ocean, whereas most from Crozet are sedentary. Instead of taking the shortest routes, which would involve a return against headwinds, migratory birds fly with the westerly winds, requiring detours of 10,000 s km. In total, migrants circumnavigate Antarctica 2 to 3 times, covering more than 120,000 km in a single sabbatical year. Our results indicate strong links between migratory behavior and fitness; all birds from Kerguelen breed biennially, whereas a significant proportion of those from Crozet, especially females, are sedentary and breed in consecutive calendar years. To breed annually, these females temporarily change mate, but return to their original partner in the following year. This extreme variation in migratory behavior has important consequences in term of life history evolution and susceptibility to climate change and fisheries.
Highlights
Extreme variation in migration strategies between and within wandering albatross populations during their sabbatical year, and their fitness consequences
During the breeding season, wandering albatrosses tracked from Crozet and Kerguelen foraged in waters around the breeding grounds to maximum ranges of c. 3500 km (Fig. 1)
When the breeding season ended in November, birds from the two populations dispersed throughout the southern oceans, but core areas were very different between populations (Fig. 1)
Summary
Extreme variation in migration strategies between and within wandering albatross populations during their sabbatical year, and their fitness consequences. Our results indicate strong links between migratory behavior and fitness; all birds from Kerguelen breed biennially, whereas a significant proportion of those from Crozet, especially females, are sedentary and breed in consecutive calendar years. To breed annually, these females temporarily change mate, but return to their original partner in the following year. Because of the reliance of albatrosses on wind for efficient flight, it is likely that migratory routes are influenced by wind conditions, and especially the strong circumpolar westerly flow[13,23] They spend the long pre-breeding period foraging over vast distances, wandering albatross chicks almost always return to their colony of origin to breed[24]. This implies that they could have overlapping atsea distributions, because in other seabirds, genetic divergence often reflects spatial segregation during the nonbreeding period[26,27]
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