Funding for this research was provided by:
Deutscher Akademischer Austauschdienst (91651080)
Received: 30 April 2020
Revised: 14 June 2021
Accepted: 17 June 2021
First Online: 8 July 2021
: All procedures involving handling of blue tits were carried out following applicable Dutch and institutional guidelines for the care and use of animals, and with permission from the Dutch Competent Authority (CCD; license no. AVD1050020184968).
: The authors declare no competing interests.