Saturday, I posed a puzzle about predator-prey signaling in a Darwinian framework, and asked for proposed solutions, and I’ve had a gratifyingly large and intelligent group of responses. So far, no one who knows the particulars has written in, but my readers offered two classes of suggestions; either one is a plausible story.
1. The signaling behavior may itself be a mate attractor and thus selected for that reason, or it may be part of a larger pattern (say, singing while flying fast) designed to attract mates. Eventually, as the proportion of starlings exhibiting that behavior rose, it acquired a second advantage as the merlins learned not to give chase.
2. The signaling behavior might have originated as a warning to conspecifics. Such behavior can be selected for if those who benefit tend to be more closely related than average to the individual exhibiting it. Again, in this story the predator signaling comes in later.
Note that both of those possibilities have testable implications.