The most credible explanation for the higher rate of survival of the large birds is:
The large birds may be the hardest for predators to attack.
This reasoning aligns with the idea that larger birds may be more difficult for predators to capture, either due to their size making them more challenging to handle or because larger birds could potentially fight back more effectively than smaller ones. The other options do not directly address the mechanics of predation or survival in a clear and logical manner.