my flock!

[Wolf]

Experience has taught me that almost anything is possible, but it is highly unlikely.

[Pajarita]

But do you think it is possible to be from the other birds?

No, it's never from other birds. For one thing, there is no bullying between flock members. Bullying implies dominance and there is no dominance in a flock. There could be fighting over a female between two males in their first season but it only happens once because, once the hen chooses, she will stay with that male and the other one accepts it and just go out looking for another wife. There could be bickering over a roosting spot or a choice piece of food but the stronger bird simply confronts the weaker bird, the weaker bird flies away and that's the end of that problem. So, no, no bullying at all and no plucking from other birds.