The thread title is not a joke.

In chicken farming the birds, typically penned together in close quarters, may peck mercilessly at one of the group, sometimes even killing the victim. Research published October 7 in Nature, and aparently quite scholarly, indicates that a chicken is more likely to become a victim if it happens to have only the recessive form of a particular gene.

So what, you say? Ah, but this is a gene that also affects the color of the bird. The dominant gene causes white feathers, but if that dominant form is absent the bird will produce more pigment and be darker-feathered.

In short, domestic chickens, typically white-feathered, will persecute their darker brethren. Further, they will do so all the more if those darker fowl are more prevalent in the group. The abstract says,

Feather-pecking in domestic birds is associated with cannibalism and severe welfare problems. It is a dramatic example of a spiteful behaviour in which the victim's fitness is reduced for no immediate direct benefit to the perpetrator and its evolution is unexplained. Here we show that the plumage pigmentation of a chicken may predispose it to become a victim: birds suffer more drastic feather-pecking when the colour of their plumage is due to a gene that controls plumage melanization, and when these birds are relatively common in a flock.

I've linked only to the abstract, since the full article requires payment, but there's a there's a free and thorough report here.

I would definitely give a failing mark for that second sentence. What the heck are they trying to say?

I see nothing surprising in the idea of birds basing their behaviour on other birds' colouring even when there is no obvious advantage arising from their colour preferences. Sexual behaviour in birds is often influenced by colour, so why not agressive behaviour also?

The occasional feather peck is unlikely to affect survival chances in the wild. It's only in the intensive farming conditions that this behaviour becomes destructive. There is no point in looking for genetic reasons to explain development of destructive behaviours that can't have been influenced by survival pressure.

quote:

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Further research is required to determine the extent to which differently pigmented plumage phenotypes, such as black or barred, predispose a bird to feather pecking and the way in which this is influenced by the social environment through frequency dependent effects.

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I suppose there must be a good reason to study the social behaviour of birds kept in unnaturally crowded conditions. It's obviously not for the good of the birds.

I'm not a pheasant plucker.

I wonder if some hens like the peckers more than others.