Abstract
The migration is energy-demanding and is expected to greatly affect the distribution of individuals over the species range and condition the choice of migratory routes. We investigated the wintering distributions and migratory flyways use of geographically contiguous populations of Lesser Black-backed Gulls (Larus fuscus) and difference in population winter age structure between migratory flyways. Recoveries of metal ringed pulli from Denmark, Sweden, and Finland were used. The results showed that contiguous populations can have distinct wintering distribution patterns and migratory flyways. More importantly, we found that depending on the place of origin, the population winter distribution may or may not show a latitudinal cline in the age structure. The population migrating via the eastern Atlantic flyway (western flyway) showed a winter age-related latitudinal cline, with adults staying at more northern latitudes than immatures. In contrast, no such pattern was found in the population migrating along the Mediterranean/Black sea flyway (eastern flyway). Interestingly, immatures within the eastern population showed a more dispersed pattern of migratory bearings. Overall, our results enhance the importance of the migration flyway in shaping the age structure of populations in the winter quarters and how it may influence the effect of other factors like sexual maturation.
Highlights
During migration, geographically distinct populations of the same species can face different challenges when moving between breeding and wintering areas
In species that are spread over wide geographical ranges, populations from the extremes of the distribution can have different migratory problems to solve and can develop distinct migratory behaviours in response to the specific ecological constraints
Within-population results evidence the existence of a variety of distribution and differential migration patterns [12]
Summary
Geographically distinct populations of the same species can face different challenges when moving between breeding and wintering areas. Ecological barriers, such as the Sahara Desert, or mountain ranges, such as the Alps or the Pyrenees, contribute to the shaping of migratory routes and the patterns of distribution of the species that have to cross them [1, 2]. In a western population of Lesser Black-backed Gulls, Larus fuscus, adults, and juveniles were shown to exhibit different migration habits and distribution patterns [18, 19], with adults staying in the International Journal of Ecology. We will expect a latitudinal population age-structure variation in the two migration flyways with adults staying more northern than juveniles in the winter range. We predicted that if sexual maturation is in the onset of age related distribution patterns, northern populations of L. fuscus should all present similar distribution patterns in the wintering area
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