Bird Watching (UK)
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QAre the Mute Swans in this picture Polish morphs? It was taken in Brockwell Park near Brixton and shows three conventional Mute Swan cygnets and two much paler ones. There is a third pale cygnet outside of view. Given the contrast, I’m tempted to ID the paler siblings as Polish morphs but am puzzled by the volume in this one family. I’m of the understanding that Polish swans are fairly rare occurrence, so your thoughts on my interpretation would be much appreciated.
AThe term ‘Polish swan’ has been applied to Mute Swan cygnets which are white (instead of grey) and have correspondingly pinkish-grey legs and feet. [Note that this is Polish as in from Poland, rather than polish, as in Mr Sheen]. The name apparently derives from some young Mute Swans imported to London from the Polish Baltic coast at the start of the 19th Century. These birds, with white feathering, were initially thought to be a separate ‘Polish’ species. The colour, or lack of it, is probably caused by a chromosomal pigment deficiency and mixed broods of ‘Polish’ and ‘normal’ cygnets are not uncommon, (depending on the number of inherited chromosomes). And, yes, you appear to have one of these mixed broods.
Why not four legs?
QMost mammals walk on four legs, at least one notable exception has evolved to walk on
two. Some have adapted (through evolution) their fore limbs into wings and can now fly, or glide. If quadrupedalism is such a successful strategy, why have no birds evolved to walk on four legs? Nick Sutton
ABirds evolved from dinosaurs. Indeed it can be argued that birds are dinosaurs; or, as at least one famous evolutionary biologist has stated, dinosaurs are birds! Modern birds evolved from four-limbed reptiles, where the fore-limbs have become extensively feathered and the hind limbs used for perching, walking etc. Even modern flightless birds have evolved from ‘winged’ ancestors.
There has not, in the evolutionary history (over tens of millions of years) of modern birds, come a time, when a bird has transitioned between using the fore-wings for flight to using them for walking. And it is hard to see how or why this would happen in the future.
Incidentally, the ‘opposite’ has occurred, with some bird-like dinosaurs and early birds having long feathers on their hind legs (as well as their fore-limbs), which may have allowed at least gliding flight.
What is this bird?
QI spotted this bird at the end of May, and thought it was a Cetti’s Warbler. Another party thought it was a Whitethroat. What is your valued opinion? Chris Farrell
AThe other party was correct, Chris, this is indeed a Whitethroat, or Common Whitethroat if you prefer. There is a certain resemblance to Cetti’s Warbler (rufous upperparts, paler underparts), but they tail is too long, there are obvious rufous fringes to the wing feathers and a white eye-ring (as well as a white throat). Judging by its brown (not grey) head, it is probably a female.
Name the owl
QI just got back from Israel where I came across this juvenile owl, but have struggled to identify it. Could it be a Eurasian Scops Owl?
AWe think your baby owl is a young Tawny Owl, John. The barring on the breast and belly, the facial disc and the overall shape and colour all look typical for this species. Tawnies are pretty widespread owls, and indeed are resident in parts of Israel.