Birds have so many enemies in common that one would hardly expect them to prey upon each other, especially in the nesting season. Nevertheless, they do.
Last summer, I watched a jay travelling along the whole length of a wire fence, looking on the ground for the nests of birds, such as the skylark. First it stood on a fence post and deliberately looked all round, examining the ground minutely from above. Afterwards it flew to the next post, and made a scrutiny of the ground there. And so on right down the whole length of the fence.
I have seen a rook in a wood watching the gamekeeper from a safe distance, hoping to discover from the mans actions some hints concerning the whereabouts of pheasants nests containing eggs.
During a recent summer, I was in a field where many hundreds of pheasant chicks were being reared in coops, under barn-door fowl foster-mothers. In these cases, of course, the old broody hens are confined in the coops, while in the daytime the young pheasants run about outside, having access to the hen through the front bars.