I'm not buying the fish egg on bird feet theory. I'm not saying it couldn't happen, but I think it would be extremely rare. I think someone already mentioned that a fish egg doesn't even have a good chance of surviving under normal conditions. This scenario puts it into astronomical porportions:
*Egg is laid (and may or may not have been fertilized)
*Egg is dislodged by a wading bird (likely mechanical damage)
*Egg travels out of water for a distance (exposure to air weakens defenses/shock from temp changes)
*Egg is shaken off the bird foot (more likely mechanical damage)
*Egg falls to the pond bottom (probable predation by insects, crustaceans, bacteria, fungus, etc)
*Egg hatches (still open to predation, must have an opposite sex/same species fish introduced in the same way, and they must live to maturity to reproduce)
The odds seem staggering to me.
OTOH, if you have a heavy inflow or outflow of water you could have thousands of small fish introduced into your pond in a day. Some of these fish could be large enough to spawn.
That's my story and I'm stickin' to it. (until I see more evidence of course)
