While bird watching at Ashdown Forest a few days ago I spent some time trying to get some good photos of some of the commoner birds occurring in woodlands. A Treecreeper kept me occupied and frustrated for some time until I noticed a male Chaffinch foraging close by in the leaf litter. I was able to approach it quite closely a few times but due to low light conditions and me setting the camera incorrectly I failed to get a really good photo of it. However, when I was checking my photos I noticed that the bird had a large growth on its left leg so I followed it and managed to obtain some slightly better images.

The photos revealed a large, warty growth on the toes and leg of this Chaffinch but it did not appear to be in any distress although it was rather unusual that it repeatedly allowed me to get very close to it as it was feeding. I have seen this type of growth before in Thailand on the legs of Paddyfield Pipit and was informed that it was caused by a parasitic mite, but I decided to do a little research online to see what the cause could be in Chaffinches.A quick look on the BTO website revealed information on these types of growths and that there were two possible causes; excessive production of skin cells as a response to infestation by mites of the genus Knemidocoptes or warty growths resulting from Fringilla papillomavirus and a little further research revealed that it cannot reliably be told which of these is the problem by sight alone as they can often occur together.

These types of skin problems can be a problem in cage birds too and there are treatments available for them but it is not practical to attempt to treat wild birds unless taking them into captivity first. Apparently this problem is quite common in Chaffinches but also effects other finches, particularly Brambling and Bullfinch and can be transmitted by direct contact and via dirty perches. This means that good bird feeding station hygiene is needed to avoid encouraging this type of problem to spread; advice on this and further information on limb abnormalities in birds is available here - Garden-bird-Finch-limb-abnormalities-factsheet.

Not a great photograph but you can clearly see the large growth on the left foot and leg of this male Chaffinch. It otherwise seemed to be in good health and its plumage is in good condition.