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Determining the links between breeding populations and the pressures, threats and conditions they experience presents a challenge for the conservation of migratory birds which can use multiple sites separated by hundreds to thousands of kilometres. Furthermore, migratory connectivity – the connections made by migrating individuals between networks of breeding and non‐breeding sites – has important implications for population dynamics. The Whinchat Saxicola rubetra is declining across its range, and tracking data from a single African non‐breeding site implies high migratory spread. We used geolocators to describe the migration routes and non‐breeding areas of 20 Whinchats from three British breeding populations. As expected, migratory spread was high, with birds from the three populations overlapping across a wide area of West Africa. On average, in non‐breeding areas, British breeding Whinchats were located 652 km apart from one another, with some likely to share non‐breeding areas with individuals from breeding populations as far east as Russia. Four males made a direct non‐breeding season movement to a second, more westerly, non‐breeding location in January. Autumn migration was through Iberia and around the western edge of the Sahara Desert, whereas spring migration was more direct, indicating an anticlockwise loop migration. Weak migratory connectivity implies that Whinchat populations are somewhat buffered against local changes in non‐breeding conditions. If non‐breeding season processes have played a role in the species' decline, then large‐scale drivers are likely to be the cause, although processes operating on migration, or interactions between breeding and non‐breeding processes, cannot be ruled out. [ABSTRACT FROM AUTHOR]

It is essential to gain knowledge about the causes and extent of migratory connectivity between stationary periods of migrants to further the understanding of processes affecting populations, and to allow efficient implementation of conservation efforts throughout the annual cycle. Avian migrants likely use optimal routes with respect to mode of locomotion, orientation and migration strategy, influenced by external factors such as wind and topography. In self‐powered flapping flying birds, any increases in fuel loads are associated with added flight costs. Energy‐minimizing migrants are therefore predicted to trade‐off extended detours against reduced travel across ecological barriers with no or limited foraging opportunities.Here, we quantify the extent of detours taken by different populations of European nightjars Caprimulgus europaeus, to test our predictions that they used routes beneficial according to energetic principles and evaluate the effect of route shape on seasonal migratory connectivity.We combined data on birds tracked from breeding sites along a longitudinal gradient from England to Sweden. We analysed the migratory connectivity between breeding and main non‐breeding sites, and en route stopover sites just south of the Sahara desert. We quantified each track's route extension relative to the direct route between breeding and wintering sites, respectively, and contrasted it to the potential detour derived from the barrier reduction along the track while accounting for potential wind effects.Nightjars extended their tracks from the direct route between breeding and main non‐breeding sites as they crossed the Mediterranean Sea–Sahara desert, the major ecological barrier in the Palaearctic–African migration system. These clockwise detours were small for birds from eastern sites but increased from east to west breeding longitude. Routes of the tracked birds were associated with partial reduction in the barrier crossing resulting in a trade‐off between route extension and barrier reduction, as expected in an energy‐minimizing migrant.This study demonstrates how the costs of barrier crossings in prevailing winds can disrupt migratory routes towards slightly different goals, and thereby promote migratory connectivity. This is an important link between individual migration strategies in association with an ecological barrier, and both spatially and demographic population patterns. [ABSTRACT FROM AUTHOR]