Funding for this research was provided by:
Deutsche Forschungsgemeinschaft (SCHM 2647/3-1, SCHM 2647/1-2)
Deutsche Ornithologen-Gesellschaft DO-G
Text and Data Mining valid from 2020-02-07
Received: 18 September 2019
Accepted: 16 January 2020
First Online: 7 February 2020
Ethics approval and consent to participate
: All procedures were approved by the Ministry for Agriculture, the Environment and Rural Areas, Schleswig-Holstein, Germany (permission numbers: V244–7224.121.9–11 (3–1/14), V244–4829/2017 (33–3/17)).
: “Not applicable”.
: The authors declare that they have no competing interests.