Funding for this research was provided by:
Bundesamt für Naturschutz (351582210A, 351986140A)
Institut für Vogelforschung - Vogelwarte Helgoland
Received: 3 May 2021
Revised: 11 September 2021
Accepted: 27 September 2021
First Online: 13 October 2021
: The authors have no financial or proprietary interests in any material presented and discussed in this article.
: Experimental procedures were approved by the Ministry of Energy Transition, Agriculture, Environment, Nature and Digitalization (MELUND) Schleswig–Holstein, Germany, license number V244-69134/2016(92-8/16).