Tim writes: the scientific name Apus apus comes from the Greek “a pous” meaning without foot. Swift legs are so small that it was once believed that they did not have any feet.
I remember the old Reader’s Digest book of birds illustrated Swift feet showing all four toes pointing forwards. But in fact the outer two toes can rotate freely to point forwards or backwards, and this condition is known as “pamprodactyly”. Most birds have three toes forwards and a hind toe pointing back, though there are exceptions, like woodpeckers. When a Swift lands at the nest site all four toes point forwards, but if you look closely at this flying bird you can only see three forward pointing toes, suggesting that the default position of the toes in flight is three forwards and one back. This photo showing the toes might be more significant than I realised as I have looked on the internet (admittedly not exhaustively) and I cannot find another photograph that shows the toes on a flying Swift. Having such short legs, they seem to keep the feet tucked inside their plumage when the fly.
If anyone’s interested I used an exposure of 1/2500 with 420mm at f5.6 (Nikon D500). And this was my best of twenty shots during an hour’s shooting over my garden on 24 July this year.
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Tim: apparently recent research showed that swifts lower their feet in flight to enable them to lose heat in very hot weather – but which way the toes point I don’t know so you pose an interesting question.