ACKNOWLEDGEMENTS
EPB was supported by funding from the European Union’s Horizon 2020
research and innovation programme under the Marie Sklodowska-Curie grant
agreement No. 8444403. CB was supported by a DFG fellowship BA 5422/1-1.
JJB was supported by NWO grant 823.01.006 awarded to Franjo Weissing and
by NWO grant 823.01.009 awarded to SV, which also covered fieldwork and
analyses costs. We thank Martijn Salomons, the late Cor Dijkstra and
many students that contributed to the fieldwork. Fieldwork was approved
by the University of Groningen animal ethics committee under license
numbers (4071, 5871, 6832-A & 6832-B) before conducting research.