Abstract
AbstractAimThe extent to which individuals from different breeding populations mix throughout the non‐breeding season (i.e. ‘migratory connectivity’) has important consequences for population dynamics and conservation. Given recent declines of long‐distance migrant birds, multipopulation tracking studies are crucial in order to assess the strength of migratory connectivity and to identify key sites en route. Here, we present the first large‐scale analysis of migration patterns and migratory connectivity in the globally near‐threatened European roller Coracias garrulus.LocationBreeding area: Europe; passage area: Mediterranean, sub‐Saharan Africa, Arabian Peninsula; wintering area: southern Africa.MethodsWe synthesize new geolocator data with existing geolocator, satellite tag and ring recovery data from eight countries across Europe. We describe routes and stopover sites, analyse the spatial pattern of winter sites with respect to breeding origin and quantify the strength of connectivity between breeding and winter sites.ResultsWe demonstrate the importance of the northern savanna zone as a stopover region and reveal the easterly spring loop (via Arabia) and leapfrog migration of rollers from eastern populations. Whilst there was some overlap between individuals from different populations over winter, their distribution was non‐random, with positive correlations between breeding and autumn/winter longitude as well as between pairwise distance matrices of breeding and winter sites. Connectivity was stronger for eastern populations than western ones.Main conclusionsThe moderate levels of connectivity detected here may increase the resilience of breeding populations to localized habitat loss on the winter quarters. We also highlight the passage regions crucial for the successful conservation of roller populations, including the Sahel/Sudan savanna for all populations, and the Horn of Africa/Arabian Peninsula for north‐eastern rollers.
Highlights
Migratory birds are potentially more vulnerable to environmental change than sedentary species because they rely on resources at a series of sites separated by hundreds to thousands of kilometres (Newton, 2004)
We demonstrate the importance of the northern savanna zone as a stopover region and reveal the easterly spring loop and leapfrog migration of rollers from eastern populations
Two autumn routes were apparent: rollers from south-west Iberia took a westerly route along the Atlantic coast of West Africa before bearing east along the savanna belt, whereas those from north-east Spain and southern France flew directly across the Sahara (Figs 2 and S1)
Summary
Migratory birds are potentially more vulnerable to environmental change than sedentary species because they rely on resources at a series of sites separated by hundreds to thousands of kilometres (Newton, 2004). A growing body of tracking studies are identifying the sites used and threats encountered by migrants during the non-breeding season. These studies reveal a range of migration strategies and patterns, including migratory divides (Reichlin et al, 2008), narrow-front (Willemoes et al, 2014) and broad-front migration (Schmaljohann et al, 2012), leapfrog migration (Panuccio et al, 2013), loop migration (Tøttrup et al, 2012) and convergence at ecological barriers (Strandberg et al, 2009). Multipopulation studies provide insight into migratory connectivity, that is, the extent of mixing of different breeding populations during the non-breeding season (Stanley et al, 2014; Trierweiler et al, 2014). Connectivity across the annual cycle has strong implications for conservation management, and its estimation is an important precondition for its effective delivery
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