Apart from the obvious flight surface feathers provide for birds, do they serve any other purpose?

I suppose the first thing they do is help us define any living animal with feathers as a bird. I'm trying hard now, in my mind, to prove myself wrong and think of a feathered animal that's not a bird, but I can't. Please let me (and the Natural History Museum) know if you can...

Feathers are a bird's insulation, they form a protective shield to the skin and they play a huge part in external appearance - which of course makes bird ID easier for us and makes spotting males and females easier; however, a feather's colour and pigments are as they are to assist courtship and amplify (during courtship) or camouflage (from prey).

Interestingly, birds in captivity, Canaries for example, can lose their natural colour which is why experienced bird-keepers introduce colour foods into their birds' diets. This suggests that wild (free living) birds are able to convert their more natural diet into values that help them retain their colours. Having said that, there's recent evidence that wild birds may be losing colour and this has been associated with a lack of lutein in birds' diet. A slight loss in a bird's colour to us would make little difference - we may not even notice; however, I wonder if loss of colour could be associated with a decline in attraction and natural selection?   

It's a lot more complex than that but, that's roughly what a bird's feathers are for. 


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