Abstract
During autumn 2016, bird ringing stations in east Sweden observed Great Tits Parus major with extremely aggressive behaviour. They attacked smaller birds such as Goldcrests Regulus regulus, killed them and ate the brain or the content of the belly. I examine with data from Ottenby Bird Observatory two explanations: the birds were exhausted after migration and very hungry or they were birds from an eastern population where aggressive behaviour has been suggested to be more common. Fat index and body mass did not indicate low energy stores and the weather was stable with wind from the east so the first explanation was not supported. Unfortunately, wing length cannot be used to differentiate between Swedish and more eastern populations so also the second explanation could not be supported. However, Great Tits from eastern parts of north Europe moult their alula earlier than birds from Sweden. The next time aggressive Great Tits are observed, bird ringers should check the moulting stage of the alula in order to determine their origin.
Highlights
During autumn 2016, bird ringing stations in east Sweden observed Great Tits Parus major with extremely aggressive behaviour
Larsson (2015) har beskrivit hur magra talgoxar visat aggressivt beteende under två dagars ringmärkning (13–14 oktober 2014) på Utklippan i Blekinge
Cramp (1989) nämner att ryska talgoxar visat ett aggressivt beteende men orsaken till beteendet nämns eller diskuteras inte
Summary
During autumn 2016, bird ringing stations in east Sweden observed Great Tits Parus major with extremely aggressive behaviour. Ringmärkare observerade också talgoxar som angrep mindre fåglar utanför näten och dödade dem genom att just hacka sönder hjässan. Både hanar och honor, vägde signifikant mindre i jämförelse med fångade talgoxar de sju föregående åren. Larsson (2015) föreslog att det troligen berodde på att talgoxarna som kom till Utklippan den 13–14 oktober hade flugit i regn och i motvind så att flygtiden från Baltikum tagit 15 upptill 20 timmar, vilket kunde förklara de låga vikterna på fåglarna.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
