Data and code for: Extreme migratory connectivity and apparent mirroring of non-breeding grounds conditions in a severely declining breeding population of an Afro-Palearctic migratory bird.

Data and code for analysing nightingale migratory connectivity Here, we include the final processed non-breeding grounds used in the analyses, obtained from GLS, GPS tags, and ringing recoveries. GLS-derived non-breeding locations for other species can be obtained from Finch et al. 2017, and specifically for other breeding populations of nightingales, these data can be obtained from Hahn et al. 2013. National ringing data are available from Euring. The data needed for the SDM were obtained from the Earth Engine catalogue and ESA CCI (2018). The presence and absence records were obtained from eBird, the African Bird Atlas, and Zwarts et al. (2023) We used Google Earth Engine and R to extract, manipulate, and analyse these data. References Finch, T., Butler, S. J., Franco, A. M. A. & Cresswell, W. Low migratory connectivity is common in long-distance migrant birds. Journal of Animal Ecology 86, 662–673 (2017). Hahn, S., Amrhein, V., Zehtindijev, P. & Liechti, F. Strong migratory connectivity and seasonally shifting isotopic niches in geographically separated populations of a long-distance migrating songbird. Oecologia 173, 1217–1225 (2013). Zwarts, L., Bijlsma, R. G., Kamp, J. V. D. & Sikkema, M. Distribution and Numbers of Ground-Foraging Birds between the Hyper-Arid Sahara and the Hyper-Humid Guinea Forests. Ardea 111, (2023). ........................................................................................ BTO would also greatly appreciate if you could fill out this very short form to tell us how you intend to use these data. Thanks in advance!