Thanks jpsdad.
I knew there was no "perfect" strategy to beat the birds, I just wanted to optimize at the design stage.
I didn't realize that bird predation was insignificant for a forage pond. Good reproductive conditions can just overwhelm the predation losses!
I guess it depends on the birds that are present. Kingfisher and Coot will take and may target preferentially the size that BG are at 4 to 6 weeks. GBH need bigger prey and I think cormorants do too. If a forage pond remains watered year round and has all manner of fish sizes in it ... it will attract a broader spectrum of predators. If the prey is predominately small, even with extensive shallow water, GBH will choose to the destination pond because it has the size of prey they need.
I once read that the minimum depth to discourage large wading birds is 2.5 ft deep. Steep sides also discourage them. Green heron, at least when I observe them, tend to hunt from the bank.
