Torchy, tough situation. The bullhead balls should be pretty easy to catch out with a net or to seine them out. You'll probably never get them all, but it's a start. Bass love small bullheads before they get their hard pectoral and dorsal spines, plus they're easy for them to catch. If you don't have any bass in the pond it's an option. How big is your pond and what type of pond are you wanting(large sunfish, combo, easy fishing etc.) You also could run trot lines in your pond. Just bait it and lay it along the bottom. You could even use your greenies as bait. Unfortunately these are 2 very difficult species to eradicate without chemicals or draining again, but even then...there is still a chance that a couple could survive. Were those fish present in the pond before it was drained? I always find the bird theory very difficult to believe due to the make-up of fish eggs. The bird would have to be extremely quick to make it from point A to point B without the thin membrane walls drying out. Most of the birds are wading birds only going out as deep as their legs are long(not getting their feathers wet often) mostly leaving only their legs exposed. So if the eggs were on the bird, they would most likely be on the legs which would not keep the eggs moist if they managed to stick to the feet during flight at all. In my opinion the odds of one egg surviving and making it into your pond and hatching are pretty remarkable not to mention how many eggs would have to survive in order to have the number of fish you have in such a relatively short period of time. Does your fish dealer even raise greenies and/or bullheads? If not, you could eliminate that option. Best of luck to you. If you solve the mystery let us know.