Discovering the migration and non‐breeding areas of sand martins and house martins breeding in the Pannonian basin (central‐eastern Europe)

The central‐eastern European populations of sand martin and house martin have declined in the last decades. The drivers for this decline cannot be identified as long as the whereabouts of these long distance migrants remain unknown outside the breeding season. Ringing recoveries of sand martins from central‐eastern Europe are widely scattered in the Mediterranean basin and in Africa, suggesting various migration routes and a broad non‐breeding range. The European populations of house martins are assumed to be longitudinally separated across their non‐breeding range and thus narrow population‐specific non‐breeding areas are expected. By using geolocators, we identified for the first time, the migration routes and non‐breeding areas of sand martins (n = 4) and house martins (n = 5) breeding in central‐eastern Europe. In autumn, the Carpathian Bend and northern parts of the Balkan Peninsula serve as important pre‐migration areas for both species. All individuals crossed the Mediterranean Sea from Greece to Libya. Sand martins spent the non‐breeding season in northern Cameroon and the Lake Chad Basin, within less than a 700 km radius, while house martins were widely scattered in three distinct regions in central, eastern, and southern Africa. Thus, for both species, the expected strength of migratory connectivity could not be confirmed. House martins, but not sand martins, migrated about twice as fast in spring compared to autumn. The spring migration started with a net average speed of > 400 km d –1 for sand martins, and > 800 km d –1 for house martins. However, both species used several stopover sites for 0.5–4 d and were stationary for nearly half of their spring migration. Arrival at breeding grounds was mainly related to departure from the last sub‐Saharan non‐breeding site rather than distance, route, or stopovers. We assume a strong carry‐over effect on timing in spring.