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Message: <blockquote data-quote="KnockerNorton" data-source="post: 1690734" data-attributes="member: 66452">Wild hybrids among passerines (perching birds) of different genera are extremely rare. Out of all the millions of Blue and Great Tits ringed in the UK over the last 50 years, I don't think there has been a single record of a hybrid.But this bird is a first-winter female Great Tit. The only thing slightly odd about it is the left flank. But this is a well-known condition, and is caused by a parasite (probably insects) eating away the ends of the feathers. This occurs on many small cavity-roosting birds, such as the tits and Nuthatches, and so probably happens at night while they're roosting. The featehrs are fluffed up in a ball, and the belly is probably in contact with the surface where the insects have been hiding. This might be an old nest in a hole, with the insects otherwise eating the fibres and feathers in that. It doesn't do them any favours, but some survive. I don't think anyone has tracked down the exact culprit, but it's the same principle as having your woolly jumper nibbled by critters in the wardrobe.</blockquote>