PICTURES: Rare sight in Watten of a special sparrow that stands out from her flock due to ‘genetic mutation’
An unusual visitor seen at a Watten birdfeeder stands out from the flock due to her pale colouring due to a genetic mutation.
The sparrow, which appears to be a female, has been regularly visiting the garden in Watten and looks remarkably different from her flock due to very light coloured feathers.
RSPB Scotland was contacted, and its spokesperson identified the condition as leucism – a genetic condition that results in a partial loss of pigmentation and is inherited.
The bird charity spokesperson said: "This beautiful leucistic house sparrow is quite an unusual spot!
“Differences like this are caused by a mutation in the genes that produce the pigmentation in feathers. The result can be birds with feathers that are unusually white, black, red or yellow. Leucism is the term given to describe a bird where feathers have become paler or white, but where eyes remain dark, while albino or albinistic birds would have red or pink eyes.
“While not a common occurrence, leucistic blackbirds and house sparrows are more often spotted than other species."
Caithness county bird recorder Rob Hughes, who runs the Facebook page Caithness Birds, said that if you look at any “decent size flock of house sparrows you’re bound to find some form of leucism within it”.
He continued: “Your picture is a ‘dilution’ condition grouped under ‘leucism’. It means that melanin cells are present (unlike leucistic birds) but produce less pigment than normal. It’s not uncommon in birds. Most people don’t notice because they aren’t looking for it, but it’s particularly common in pigeons, for example.”
Rob said he saw a ‘browning’ Guillemot with similar colour that flew past Nybster recently. “I’ve seen a few house sparrows with it, but starlings are another regular one for it too.”
According to the British Trust for Ornithology (BTO), the lack of pigment can cause the feathers to be much weaker than other birds of the same species. “However, the chances of survival for leucistic birds are low, as their distinctive whiteness can make them a target for birds of prey. In some scenarios, leucistic birds also may not be recognised or accepted by a potential mate.”
The BTO further states that the colouring is present throughout a bird’s life and does not change with age.
“Far more common than leucism is 'progressive greying', which is acquired rather than inherited. Progressive greying sees the progressive loss or failure of pigment cells with age, although this can also be caused by physical disorders. From the onset of the condition, the bird will gain increasing numbers of white feathers after every moult.”
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