Birdwatch News Archive
Partially leucistic Blackbirds like this male are occurring more than might be thought, according to the newest BTO survey. Photo: HTO (commons.wikimedia.org).
The not-so-black birds
Posted on: 18 Jan 2012
A new BTO survey has revealed the extent of abnormal plumage among common birds, and the call has gone out for more observations.
Across the country, householders have been recording Blackbirds and other species with strange white markings. The condition, commonly referred to as leucism, is one of a number of plumage abnormalities to have been reported through the BTO Abnormal Plumage Survey, preliminary results from which have just been published.
In less than a month, the survey has clocked up nearly 700 sightings, encompassing more than 35 different species. Three quarters of records have been of leucistic birds and, of these, nearly half have been Blackbirds. Leucistic birds may be confused with albino individuals, but the latter have pink instead of dark eyes, and only account for 12 per cent of survey records to date.
It is not yet clear why Blackbirds appear to be particularly affected. It could be that they are unusually susceptible to the condition, though being black or, in the case of female Blackbirds, dark brown, any light-coloured feathers would show up particularly clearly. Indeed, several other species with all-black or mostly black plumage have been spotted with white feathers fairly often, including Carrion Crow (49 records) and Jackdaw (40).
Many other strange-looking birds have also been seen. Of the 28 melanistic individuals recorded - that is, those which have an excess of dark-coloured feather pigmentation patterns - almost half have been Great or Blue Tits, with their normally white cheeks and yellow bellies becoming dark-coloured. Other fascinating abnormalities have included a family of four chocolate-brown Jackdaws in Co Antrim, a Greenfinch with orange feathers in the West Midlands and a Goldfinch with an orange rather than red face in East Sussex. An all-white Starling was seen in Prestatyn, north Wales.
Dr Tim Harrison, of the BTO Garden Ecology Team, commented: “The diversity of species recorded through the survey is impressive, ranging from common garden birds such as House Sparrow and Chaffinch, to less frequent visitors such as an all-white Common Buzzard in Aberdeenshire and a leucistic Coot in Norfolk. On a handful of occasions, birds have looked so unusual that participants have simply had to write ‘species unknown'."
He added: “The most northerly record to date has been from Shetland, where there was a report of a Blackbird with white feathers around its eyes, making it look as though it is wearing spectacles. The most southerly record has been a leucistic House Sparrow seen last year on St Mary’s, Scilly. If you have ever seen a bird with unusual plumage in your garden, please let the BTO know.”
To take part in the Abnormal Plumage Survey, visit www.bto.org/gbw or telephone 01842 750050 for a paper recording form.
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