One of the reason, perhaps the most important reason is the flock. Not all birds live well together. I want my flock to live well and in peace. I will remove birds to achieve that.
What rather appalls me, is people who 'love' their birds too much to cull or remove one, so that they live together fighting, pulling feathers and tearing holes in each other, like that is a good thing?
Animal husbandry is keeping animals well. Always solve for peace in the flock. Often times, removing a bird is necessary to achieve that.
Mrs K
This is so perfectly said, I couldn't agree more!
Personally, I feel very sensitive about my chickens emotional states.
I hate to see a bully. Just hate it. Most cockerels are bullies.
I feel grossly responsible, being that I am the one controlling the fact these birds have to live together. In the wild they could go join another flock. But even free range domestic birds are limited in their social choices by food availability and lack of other roaming flocks.
I once kept a large rooster flock for about a year, with a tall fence separating them from the main flock. The roos could go all the way out to pasture to browse, but they chose to hang out next to the hens.
One day a little leghorn pullet that was about to come into lay, exhibited a fairly normal behavior for pullets of that age and was searching around for nesting locations. Leghorns fly pretty well, so she made it over the fence.
Those cockerels swarmed her. They held her down, ripped feathers out of her neck, took turns jumping all over her... not even letting her up for a moment. I saw them doing this through the window and ran out as fast as I could, but given the distance and various obstacles it took me a couple minutes to get there. By the time I did her comb was torn and bloody and when I shooed the roos away she would not even get up. She was in shock. She did not deserve what happened to her. This may be an extreme example, but it's far from rare...
Many many people getting into chickens think they are being nice by allowing excess roos to stay. They are really just transferring the suffering around the flock. Innocent hens get attacked, held down, pullets get violated before they're of an age... and too many people are blind to the suffering they are facilitating, because it's not expressed in human terms.
I'm always surprised when I see people post pictures where the hens have bald backs and they talk about it like it's normal or just aesthetic. Feather quills are attached to nerve endings, that's how they feel through a thick layer of feathers. Each and every feather hurts when it's pulled out (except molted ones), so a whole back full is like posting a picture of someone's back after a flogging. Probably equal in pain.
So this is the stuff I feel emotional about. I could care less what dead bodies don't feel anymore, or how they're used / not.
I have trouble with culling because of their fear. But we get it done (my mom handles the hard part, I do the catching, lol).
What's essential is that those roos aren't around anymore to turn my flock into some prison style gang of misery.
I pick 1-3 cockerels each season who show kind behavior to the hens and respectfulness to humans. I'm going to breed for perfect temperament if nothing else. At the end of the season I find homes for those nice ones. If some of the extras are nice, I find homes for them too. I've done it this way for 3 years now. But if he's at all picky of the others I don't mind sending him to perdition.
Since this is a long-term breeding project, I also rehome hens. Haven't culled any that were not injured (one was scalped down to the brain by a nasty cockerel). Some hens have a sweet enough personality or contribute (broodies) that they get to stay, our oldest is 5 years old and when she does lay it's the wonkiest egg ever. But she talks to us through the fence, and even though she's actually a bit annoying, she has so much personality and I worry that another home wouldn't value that about her so she gets to stay forever.
TLDR: I have a merit system.