Looking at this from the positive side, the paper shows the birds can respond rapidly.

And there was no doubt that the bird had responded to that need.

That one bird never responded again, nor did he appear.

Such birds will also occasionally respond to a crow call.

European birds do not respond to latter two song variants.

As this thought passed through his mind, he felt the hands tighten around him, and realized that the bird was responding to his will.

The birds responded quickly and the population reached more than 250 by 1975.

It probably isn't worth persisting much longer than that, because if a bird doesn't respond by then, it's never likely to.

Other identical birds respond to the call and come down from space like comets.

However, in other parts of the world, birds have responded differently to the same or similar tests.