" 'The formula that describes when an individual [bird] should forgo its own reproduction and instead help its relative reproduce.'
One formulation of this idea suggests helping should be favored when rB > C, where r is the genetic relatedness of the individual and its breeding relative, B is the additional number of offspring this helping behavior will add to the relative’s reproductive success, and C is the cost to the helper in the form of offspring that they can’t produce themselves if they invest instead in helping their relative." *
Got that? Me either. But I think what he's trying to say is this: if a bird can help produce more birds with genes similar to his by helping his family than he can produce by having his own family, he helps. If Hamilton's correct, however, the question remains. How does the bird tell in advance which will work out best? Yes, I know we keep finding birds are smarter than we think. But pardon me? No way they work out the math on this. : )
(See also Bird-nerd-words: Bird-Altruism : )