In a game theoretic framework we might say that the payoff matrices for the birds and bees are different, so of course we’d expect them to adopt different strategies.
Yes somewhat, however it would still be best for all birds if they had a better collective defense. In a swarming attack, none would have to sacrifice their life so its unconditionally better for both the individual and the collective. I agree that inclusive fitness is pretty hard to control for, however perhaps you can only get higher inclusive fitness the simpler you go? e.g. all your cells have exactly the same DNA, ants are very similar, birds are more different. The causation could be simpler/less intelligent organisms → more inclusive fitness possible/likely → some cooperation strategies opened up.
Yes somewhat, however it would still be best for all birds if they had a better collective defense. In a swarming attack, none would have to sacrifice their life so its unconditionally better for both the individual and the collective. I agree that inclusive fitness is pretty hard to control for, however perhaps you can only get higher inclusive fitness the simpler you go? e.g. all your cells have exactly the same DNA, ants are very similar, birds are more different. The causation could be simpler/less intelligent organisms → more inclusive fitness possible/likely → some cooperation strategies opened up.