Jason,
The reference I saw used that study as a reference. The experiments were originally conducted in Germany I think. Pike are native there.
I've yet to see inefficient bird digestion. What I have seen is that they typically expel feces that looks nothing like what they ate. Can't really speak for ducks specifically but I wonder how it could be possible that fish eggs might survive the GI tract of a duck OR other creature. That is why I referred to it as an adaptation. Pike wouldn't have had to have developed the adaptation for pike to possess the adaptation. If it really can happen, (I assume the referenced work is legit), then it probably developed in more primitive life and may be an inherited adaptation that is shared by other animals as well. Eggs are adapted to resist penetration by more than one male gamete so it may not be too large of a stretch that life developed a strategy to protect eggs from digestion and to aid in their distribution.
Look, I think we've much to learn and much of what we will learn just might amaze us.
