Meier, Christoph M.
Karaardıç, Hakan
Aymí, Raül
Peev, Strahil G.
Bächler, Erich
Weber, Roger
Witvliet, Willem
Liechti, Felix
Funding for this research was provided by:
Swiss federal office for the environment (grant UTF 400.34.11)
Wolfermann-Nägeli foundation
Article History
Received: 24 July 2017
Revised: 21 December 2017
Accepted: 23 December 2017
First Online: 26 February 2018
Compliance with ethical standards
:
: Birds at Swiss colonies were caught regularly for monitoring three times a year already before our study had started. For this purpose, the entire colony was captured and each individual’s identity was recorded. This was done at night when birds attended their nests for roosting either in the season before eggs were laid or in the season after juveniles had fledged. Handling time per monitored bird lasted 1 min. We used some birds treated this way as our untagged control group. Attachment of geolocator was at the same time as the monitoring in autumn and extended handling time for those birds by approximately 5 min. The majority of devices were recovered during the monitoring sessions in the following spring. Few devices also were discovered later on in the same year during additional monitoring of the laying and breeding process at the colony. Devices were attached with a body harnesses like a backpack. They were strapped around the wing and the two straps connected on the ventral site using a soft static cord of 1-mm diameter. The size of the harness was individually adjusted in the field. The heaviest logger did not exceed 1.8% of the bird’s body weight. Loggers were attached under a ringing licence of the Federal Office for the Environment FOEN and ethical approval of the veterinary office of canton of Aargau under the licence 75658. Tagging of birds in Bulgaria, Spain and Turkey was done according to the Swiss protocol at the same when the monitoring scheme was introduced for the first time in these colonies. In Spain and Turkey, only a part of the colonies could be accessed by us. There, birds were caught either on the outside of the colony by using mist net or at a different times in the year during the nest provisioning phase.For the birds equipped with tags, the recapture rates at the Swiss colonies (Baden and Lenzburg) were 81%, in Turkey 50%, in Spain 75% and in Bulgaria 30%. Control birds without a tag had return at rates of 70 and 33% in the Swiss and the Bulgarian colonies, respectively (no significant difference to tagged birds; Chi-square test:χSuperscript removed = 0.09, df = 1,p = 0.76). No feasible control was available in the other two colonies because of the restricted access. The difference in recapture rates between colonies was mainly due to different nest fidelities of the birds at different colonies and the presence of non-breeding birds (probably second-year transient birds) that gather at the colony during roosting.
: The authors declare that they have no conflict of interest.