Blackbird with yellow head spotted in Shropshire

Yellow headed blackbird.
March 2011. These images were sent to us by M. Sever from Bridgnorth in Shropshire. It was suggested that the bird might be exhibiting Xanthochroism, but closer inspection apepars to reveal that the birds head is bald. But that doesn't explain the odd yellow head; our guess is that it a diseased bird, but we are struggling to explain the strange look.

Leucism (or Leukism) 
Leucism is a very unusual condition whereby the pigmentation cells in an animal or bird fail to develop properly. This can result in unusual white patches appearing on the animal, or, more rarely, completely white creatures. 

Click here to see our gallery of albino and leucistic animals and birds.