DavidHowdon's picture

Pied Crow

Observed: 15th October 2009 By: DavidHowdon
Amateur Entomologists' SocietyLondon Natural History SocietySelborne Society
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1567 Carrion Crow D 08
1567 Carrion Crow D 09
Description:

A Crow with a lot of white feathering. I understand that this is due to a dietary deficiency and is relatively common in corvids (certainly see plenty of patchy crows around here)

Identifications
Species interactions

No interactions present.

Species with which Carrion Crow (Corvus corone) interacts

Comments

RHoman's picture

Causes of white feathers

There is a detailed review of the possible causes of such white feathers in an earlier iSpot post here:

http://www.ispot.org.uk/node/4725

If it is dietary,then the bird might loose the white in its summer moult. The indication that there are "plenty of patchy crows" in the area might support the view that it is genetic. Unlikely that all the CCs in that urban area suffered from some dietary defect?

Robert Homan

DavidHowdon's picture

Diet or genes

Not sure, my understanding is that crows tend not to spread to far from a roost 5-6 miles I seem to recall. In an urban area where I got these it seem plausible that there are food sources (tips, dustbins etc.) that are quite unnatural so a significant proportion of the local crows could be exposed to a poor diet.

RHoman's picture

Diet or genes

Without wanting to appear flippant - is a poor human urban diet equivalent to a poor urban corvid diet? If tips are a source of poor diet than thousands of gulls, crows and starlings in Gloucestershire have got it wrong.

Robert Homan

DavidHowdon's picture

Poor diet

It is not necessarily the case that a poor human diet will be a poor avian diet, but it does seem at least worth speculating (which is all I can do not being a full time ornithologist able to do research) that a bird evolved to live in one set of conditions will be less than perfectly adapted to other (urban) conditions.

My central point however, not perhaps made clearly, is that as most of my local crows feed locally a local deficiency in necessary minerals / vitamins / whatever could well account of a significant number having the same dietary deficiency. So I don't think it is possible to eliminate this explanation from the evidence I mentioned (although for completeness this is not evidence that the white feathering is not genetic in origin).

RHoman's picture

A way to an answer?

I'm sure it isn't possible to eliminate diet and the other iSpot discussion doesn't seem to come down one way or another on diet v. genes.
If the crow is faithful to a particular area then future observations might show one way or another if the bird shows a propensity to "change colour"?

Robert Homan