Foot diseased chaffinch Warwickshire 09

Foot diseased chaffinch Warwickshire 09

Observation - Foot diseased chaffinch Warwickshire 09. Description: 2009 I observed several of my garden chaffinches with growths on their feet - this one was too sick to resist my photographing it, and later died. I have so few chaffinches at the bird table now, and yet plenty - green & gold finches. What is the cause?

2009 I observed several of my garden chaffinches with growths on their feet - this one was too sick to resist my photographing it, and later died. I have so few chaffinches at the bird table now, and yet plenty - green & gold finches.
What is the cause? (I asked RSPB but never had a reply, so, glad to hear about ISpot on Radio 4)