This MISTLE THRUSH must have been a particularly white-looking juvenile but with regular colouring to its new adult feathers. It appeared both obviously white-headed & small-headed even at distance due to its moult. It showed regular adult plumage below the shoulders, very white juvenile feathers across the chest & speckled through the mantle, & moulted out juvenile head feathers with adult feathers yet to grow through.
(Thanks to Samuel Perfect for noting that particularly white juvenile feathers do not necessarily mean the bird shows any leucism.)
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| White-headed Juvenile to Adult moulting MISTLE THRUSH at Gadebridge Park |
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Hi Veloraptor,
ReplyDeleteHope local patching is going well. I think the white speckling that's just showing on the side of the mantle are just older juvenile feathers and the white-headed look is down to a near total lack of fully grown feathers on the head as opposed to leucism (hence the small-headed appearance too). The white tips to the feathers growing around the head are probably all that's showing so far but the browner bases will develop soon I think, like this one http://www.flickr.com/photos/8793530@N03/3729918527/
cheers,
Samuel
Hi Samuel, I hope you are well. Quite quiet at the moment but things starting to get moving again, & just enjoying any time I can get in the outdoors. I like your thinking, & the whiteness (& it's obvious difference against the rest of the bird) put me off thinking about the juvenile to adult moult, though this bird definitely has the whitest head of any example I can find, I agree that the speckles on the mantle are old juvenile feathers only they were absolutely pure white & again the whitest example I can find, particularly where the adult feathers show it is not an overall pale individual. If you look at the band of feathers between the short head feathers & the regular adult feathers you can see that they are regular length but still obviously white against the feathers lower down, but then the spots say they are juvenile feathers too. You are right & this bird must have been a particularly pale juvenile that is moulting into a regularly coloured adult. Thanks Samuel, not sure why I didn't realise this myself! Will have to update the post.
DeleteKind Regards, Dan.