|Juvenile Blue Tit with the a bill deformity. Ipsley Alders Nature Reserve, Mike Barstow|
Whilst ringing at Ipsley Alders Nature Reserve, Redditch, Mike Barstow retrapped a Blue Tit on 25/11/2013 that he previously ringed on 19/01/2012 with no deformity noted. This bird now had a severely deformed bill (below). The bird appeared healthy with good plumage, muscle and even had a trace of fat. There are therefore two birds (above and below) that have been recorded at this site which have developed a beak deformity within a few years.The research continues.
|Adult Blue Tit. Ipsley Alders Nature Reserve, Mike Barstow|
|Measuring bill length to investigate growth rate for future captures- Mike Barstow|
Types of beak deformities in the wild:
- Crossed mandibles: similar to that of a Common Crossbill perhaps caused by slight asymmetry of the jaw. Straight beaks have been recorded as a deformity in Crossbills.
- Decurved upper mandible: can occur when the tip of the lower mandible is damaged so that the beak does not close correctly.
- Upcurved lower mandible: may occur when the tip of the upper mandible is missing (i.e. broken off).
- Elongation of both mandibles: produces ‘Curlew-type’ beaks, although the degree of curvature varies considerably between individuals.
- Bent to the side: seemingly uncommon, with one or other mandible warping sideways.
- Gapped: where the upper and lower mandibles do not close fully leaving a visible gap.