I have dealt with a large number of birds, including magpies, with bill abnormalities over the last decade or so and the prime reason appears to be trauma. Some have tried to beat the mouse trap others have simply hit glass or MVs. Many have presented with other injuries and the bill damage is an old injury – confirming other correspondents observations that they can survive.
The bill does not generally re-grow. Bird bills are composed of a number of outer layers of keratin over partly calcified keratin fibre structure which has a blood supply virtually to the tip. It is analogous in a rough way to your finger nail in that the keratin (your nail) grows continuously off a bone and flesh structure which supply’s both reinforcement and a blood supply to renew the keratin layer. The difference is you finger grows out in one direction while the bill grows from the inside. This is why bird’s bills often appear flaky at the surface as the older keratin peels or wears away.
Keratin is a protein (the same as feathers and hair) and constitutes most of the bill’s surface it is not a product of calcium consumption beyond some calcium on the underlying bone fibres. Bill re-growth only occurs when the underlying fibres and blood vessels have not been badly compromised. Birds with large bill cracks or where the layers of keratin have been stripped have reasonable prognosis of full recovery. Those where the bill has been sheared, bent to the point of stopping blood flow, or punched to the same effect will not general re-grow their bill – hence the magpies observed. For some species whose foraging is dependent on a perfectly functioning bill the injury is a death sentence (many parrots but particularly small ones with specialised food preferences) while other will cope reasonably well.
Chris Lloyd
Logo v5
===============================
To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) to: birding-aus-request@vicnet.net.au
http://birding-aus.org ===============================
Hi Gary, Some foot deformities are caused by parasites. Glenise
My wife reminded me that our resident magpie with broken top mandible also has a club foot, circumstantial evidence for deficiency in diet, although of course the two may be unrelated. Bird is healthy.
Gaz
===============================
To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line)
http://birding-aus.org ===============================