While I was out ringing the rapidly growing chicks at SDU this weekend I came across something unusual, and very exciting! When I reached box 82, on the edge of the woods, I had a quick look in to ensure the chicks were large enough to ring. All looked good and I began the process of removing chicks one at a time to ring them. I was running on autopilot, but something stopped me after the 3rd or 4th chick. I picked out a chick which was very small in my hand in comparison to the others. It isn’t unusual to see a age or development difference within a single brood. In some situations the smaller, less developed chicks have hatched one or two days later than their older bigger siblings. But this chick felt completely different.
I turned off my “autopilot” and had a closer look. To my amazement the chick was not a Great tit (musvit) like it’s brothers and sisters, but a Blue tit (Blåmejse). There were 9 chicks, 8 Great tits and one Blue tit. This is the first time I have observed a mixed brood, but it seems it’s not a unique occurrance! A long running nest box project in Wytham Woods, close to Oxford in England, has also reported a mixed brood in one of their nest boxes recently. The parents (both Blue tits) are taking care of 6 Blue tits, and 3 Great tits! We will keep a close eye on this box and try to find out who the parents are!