Saturday, July 13, 2019
Shibden Park
As I approached the lake at 0945 I saw a Great Egret flying above the water. It did a couple of circuits below tree height, then departed over the trees to the southwest.
The white cygnet has pale legs, and a pale bill (contrast bill of the normal cygnet at top of first picture). But it has some brown in the plumage, so does this mean it's not a Polish Swan? Note: Thanks Andy for the reference to the BB article on Polish Swans ( britishbirds.co.uk/article/polish-mute-swans/ ); the photo with this article shows a bird with a similar amount of brown to ours, so ours looks good.
4 comments:
Fantastic find in the most unlikliest of settings!
Well done with the Egret Peter.
Later seen at Cromwell Bottom then flying off towards Elland at 16:10
Thanks very much Charlie and Dave. Re the swan, Andy's 2016 article mentioned that Moss Taylor in Norfolk was compiling a national survey of Polish swans, and wanted records. So I sent my photos to Moss, and he has kindly replied and confirmed that ours is one. However, his survey has finished, with the results in a very detailed BB paper on Polish swans: British Birds 111:10-24 (Jan 2018). The sex chromosomes in birds are W and Z (not X and Y), and contra to mammals it is the male that has 2 the same, ZZ. A gene on the Z chromosome controls melanin production. If this gene is faulty - and the bird does not have another normal one - melanin production is impaired: the Polish variant. Therefore, a Polish swan with normal parents will be female, with a father having one faulty Z chromosome.
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