gct[3] - spotty

A male blackbird [Turdus merula] with a few grey and white feathers.

This is a case of Leucism, sometimes also termed partial albinism.
Leucistic blackbirds can have very variable amounts of white plumage, it is estimated that about 1 in 30,000 birds display this characteristic.

Most years we seem to spot an example or two of this in "our" blackbird flock.