Funding for this research was provided by:
Vetenskapsrådet (621-2010-5584, 349-2007-8690, 2017-03937, 621-2007-5930, 621-2013-4361)
Bulgarian Academy of Sciences (DO02-277)
Received: 3 January 2020
Accepted: 5 May 2020
First Online: 29 May 2020
: The samples were collected according to legislation in the each of the different countries. An ethical permission from Lund-Malmö Djurförsöksetiska Nämnd (M45:14) was given to SB for collecting blood and feather samples in Sweden in association with mist-netting and ringing (SB Swedish ringing license nr. 555). Feather samples from Portugal were collected under the licenses 86/2009, 122/2009/CAPT and 92/2010 issued by CEMPA/ICNF. Blood samples from Bulgaria were collected under permission 213/26.6.2009 issued by Ministry of Environment and Water of Bulgaria.
: Not applicable.
: The authors declare that they have no competing interests.