èƵ recently ran an article about crows making up after a fight, or keeping their distance from another crow they had beaten (6 January). So how do crows tell each other apart? They look alike to me.
• Crows look alike to you because you can’t see in the ultraviolet. Most birds can, and the plumage of crows, which to us looks mostly black, is elaborately detailed when seen under ultraviolet light.
There are also many matt and iridescent colours in corvid feathers. Seen close up, even with human eyes, the plumage is marvellously patterned.
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Differences in plumage colouration are used by birds in mate choice, and probably also in social interactions in flocks. Corvids also vary individually in caw sound, so they can tell who is who even with their eyes shut.
Rowan Hooper, London, UK
• It is possible that the reason we – as adults, at least – can’t tell crows apart is due to “perceptual narrowing”. As humans, we don’t need to tell crows apart, so lose the ability to do it, instead developing the ability to recognise human faces. Studies of babies have shown that at 6 months old they have the ability to tell monkeys apart, but lose this by 9 months old, as their brain learns that skill isn’t needed. Presumably, a child who grew up around monkeys would retain it.
Something similar happens even with our own ethnicity, which is why people can find it harder to tell different ethnicities apart than they do their own.
Other crows are perfectly identifiable to the crow brain, allowing them to engage in the kind of social activity described.
Cath Ferguson, Glasgow, UK
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