New paper on nightjar migration
The European nightjar Caprimulgus europaeus is a nocturnal aerial insectivore that breeds across Europe and Asia during the northern summer. The species´ nocturnal habit forces it to overlap the daily timing of fuelling and flying, which theoretically could reduce its migration efficiency relative to other Afro-Palaearctic migrants that perform nocturnal flights and allocate the daylight hours to fuelling. Until recently, little has been known about the migration routes and migration strategies of the nightjar, although a new British study has shown that three British breeding nightjars wintered outside the expected wintering range.
To test a set of hypothesises on nightjar migration, a population of nightjars breeding in south-eastern Sweden was subjected to a study where geologators were used to track their movements. In 2011-2014 a total of 78 geolocators were mounted on different birds, of which 19 were retrieved. 12 of these contained light-data that could be used to reconstruct complete tracks from 12 different individuals.
In conformity with the British study, Norevik et al. found that the birds indeed wintered almost entirely outside the formerly believed wintering range of the species. Unexpecterdly, it was also found that the migration speed was faster in the autumn than in the spring - thus adding the nightjars to the minority of species with slower spring migration than autumn migration.
Morover, the temporal patterns that was found within the annual cycle indicate that individuals follow alternative spatiotemporal schedules that converge towards the breeding season. The positive relationship between the spatially and temporally distant winter departure and breeding arrival suggests that individuals' temporal fine-tuning to breeding may be constrained, leading to potential negative fitness consequences.