21/03 Greenham Common Postscript

 Unusual bill on a female 1st calendar year Great Tit

At yesterday's ringing session of the 20/03/2022 I forgot to add this photo of a Great Tit we ringed that had an elongated upper mandible. It looked as if the lower mandible may have been elongated possibly it had crossed but had snapped off.

We have captured bird with similar bills before both of this species and Blue Tit, sometimes the extended upper and lower mandibles cross. It appears not to affect the birds ability to feed as they are usually within the expected weight range. This bird at 18.7gm was a little on the heavy size for a female Great Tit and appeared to be in good condition. Not sure what the survival rate might be though. The bill of birds is composed of  similar material to our nails so presumably these birds are feeding in a way that does not subject the mandibles to normal wear and tear and/or they possibly have an abnormal growth hormone etc. A ringer recently posted on the internet that a bird with similar extensions to the bill was subsequently re-trapped with a normal bill configuration a few months later. We have a note of the ring number and will look out for it in the future.