It was a nice digression, though. And it is good to be warned of odd people... ;)
The birds have a number of different signal calls. The warning signal usually is a short, high-pitch chirp. One can easily imagine that the natural selection has guided the warning call to be difficult to get a bearing on. The predator will hear it, but is not able to home in on the call.
Counterproductive as it may seem, I understand the designers that put a "Low Battery" warning light on their product. I've been driven crazy by the once-an-hour chirps, too.
(no subject)
It was a nice digression, though. And it is good to be warned of odd people... ;)
The birds have a number of different signal calls. The warning signal usually is a short, high-pitch chirp. One can easily imagine that the natural selection has guided the warning call to be difficult to get a bearing on. The predator will hear it, but is not able to home in on the call.
Counterproductive as it may seem, I understand the designers that put a "Low Battery" warning light on their product. I've been driven crazy by the once-an-hour chirps, too.