'Yellow billed' Moorhen

[gabrieljamie]

I saw this Moorhen lacking red pigment on the bare parts at the entrance lake to the London Wetlands Centre today. As well as having an all yellow bill and frontal shield it also lacked the red colour to the base of the legs.
Here is a link to some photos of it:
http://www.flickr.com/photos/23555819@N07/2304860837/in/photostream/
and
http://www.flickr.com/photos/23555819@N07/2305658886/in/photostream/
I had never seen a Moorhen looking like this before and was wondering whether anyone else had. Is the lack of red pigment on the bare parts a relatively regular phenomenon amongst birds?

[john robinson]

Jamie
Looks like there is a definate lack of colouring. It does happen from time to time.
By the way when I went to your link it took ages to get there, but I am not on broadband. Maybe an idea would be to upload a pic as an attachment with your post on this forum.
Chers
JohnR

[Graham Etherington]

The lack of any red pigmentation is called 'anerythristic' and is most commonly found in reptiles, especially snakes (mostly, I believe, as regularly occurring colour forms). Interestingly, the intensity of yellow on Moorhen's bills has been found to be proportionally related to breeding success; the intenser the yellow, the greater the success.

[marklhawkes]

See also this thread, probably relating to the same bird

http://www.birdforum.net/showthread.php?t=100786&highlight=moorhen

Some interesting comments about Coot x Moorhen hybrids too.

[gabrieljamie]

Thanks a lot for all the information.

I am interested to see what the offspring of this bird would look like. Do such pigment abnormalities tend to be caused by a single gene variant and if so does the allele 'for' no red pigment tend to be recessive or dominant?

It would be interesting to know whether, as what Graham said would suggest, the intense yellow of this bird's bill has an affect on its reproductive success. If the effect is favourable though, and the yellow bill does not make such birds any more vulnerable to predation, then would you not expect to find the gene 'for no red pigment' to be more prevalent in the gene pool of the Moorhen?

[Graham Etherington]

Thanks a lot for all the information.

I am interested to see what the offspring of this bird would look like. Do such pigment abnormalities tend to be caused by a single gene variant and if so does the allele 'for' no red pigment tend to be recessive or dominant?

It would be interesting to know whether, as what Graham said would suggest, the intense yellow of this bird's bill has an affect on its reproductive success. If the effect is favourable though, and the yellow bill does not make such birds any more vulnerable to predation, then would you not expect to find the gene 'for no red pigment' to be more prevalent in the gene pool of the Moorhen?

That's taking the yellow bill is a genetic trait. If it occurs due to environmental factors, then that would be different. A bright yellow bill might just indicate that the bird has managed to feed well, remained healthy, and is in good condition.

[gabrieljamie]

If it were an environmental factor would you not expect it to be far more common amongst Moorhens. Also you would expect to find intermediates, eg birds with 3/4 yellow on bill and frontal shield and 1/4 red, depending on how strong that environmental factor was. Do you know if such individuals exist?

Anerythristic corn snakes have their red colour bred out through selective breeding, so, in that case it is genetic.