Great thread that brings up some wonderful solutions and interesting food for thought.
Personally we have an assortment of small ornamental ponds with frogs and fish that attract their fair share of predation. Everything from herons and owls to possums, cats, coons, foxes and of course snakes. We're in a suburban area of 1-2 acre lot housing that is bounded by 30 acres of woods, very near several hundred square miles of undeveloped and forested parks, and thousands of acres of farmland beyond that. Even though we're only minutes from the interstate and shopping malls we see more wildlife in a day than you would believe. The deer herds in particular love grazing on suburban landscapes and we've even had visits from some coyotes of late.
The pond fish and frogs have been holding their own with the help of a bird net cover and a ring of chicken wire around the perimeter, but even then we still have the occasional visitor drawn by our amazing toad and tree frog population, (after a rain it sounds like the anvil chorus). Since we're near the gathering point for a good bit of the watershed as well, our area is a prime gathering area for critters looking for food and drink. My concern has always been that the rule of unintended consequences always seems to win anytime humans attempt to alter natures order. I would say the same about governments trying to engineer things but that's fodder for a different area.
Many of our neighbors feed their own pets, as well as a feral cat population and any wild mammals, by leaving pet food in bowls outside. The very same folks then scream when they discover that they have rats (usually the same not so brights that aren't too diligent about cleaning up after their dogs as well). Next thing ya know they're calling county animal control 'cuz they have possums, coons and foxes visiting, and of course there's the weekly frantic screams of our more urbanized neighbors when they encounter the odd garter or black snake. Unfortunately the latter are usually dispatched with all manner of shovels and hoes before I can manage to relocate them to friendlier digs.
I guess the point is that nature has its own way of dealing with population control. Where food and water is abundant, life will flourish, including the varieties that we oft times consider pests. A few years back I went on a possum relocation crusade 'cuz they insisted on finding ways into the ponds. After trapping and moving a half dozen or so we began to notice previously non-existent rat borrows. Seems that possums are one of the rat's biggest natural predators, and I had unwittingly removed a vital link in the food chain. Rats gestate and reproduce at such an alarming rate that they can and will gladly fill any void in the chain given half a chance. After spending the rest of the summer chasing them down and eradicating as many as possible we noticed several new red tailed hawks and an owl had taken to hunting the area. Thankfully this worked to check the rat explosion along with reducing our squirrel herds. Into this menagerie we intend to start our small flock of laying hens (sans rooster at first just to kind of desensitize our citified neighbors and get them used to some free fresh eggs...then we'll see how they take to the new alarm clock).
So when we decide that we know best and start fiddling about with the natural order we invariably cause a shift that maybe we hadn't really thought completely through. My Doc lives in a similar area just across the reservoir from us and has had to resort to a completely enclosed run to keep the hawks off of his flock. Racoons are constantly testing his perimeter and even with daily vigilance he has still had to endure several bloody invasions. So far the answer has been to keep upgrading the perimeter defenses, but it seems that nature continues to adapt. Even with a chicken wire roof he has had the hawks land within yards of him and begin trying to pull the wire apart to get to his birds. Close enough that he could have swung a shovel on it (had he been willing to tempt fate and the Federal law that protects the hawks). I'm not saying I have the answer 'cuz everybody has their own unique set of circumstances to deal with. Thankfully the copperheads 'round here stay well down in the rocks closer to the river, and the Eastern Diamondbacks are a lot more shy of civilization, but that doesn't mean we won't someday see them.
Love the re-purposing of the minnow traps and I intend to set a few just to get an idea of our snake population, if any. We recently installed a video surveillance system to keep an eye out for two legged varmints but have been amazed at the number and variety of night time visitors that we never imagined being so bold (everything in the neighborhood regularly visits our BBQ grill). So while the toads keep me awake some nights and the bats scare the crap out of the wife and kids, I don't miss the skeeters. The neighbors still feed and house the rats (they also love firewood stacks that sit right on the ground) so the possums occasional visits will be tolerated. I'm not sure what our foxes are thriving on (we have dozens) but I don't intend to do away with them unless and until I'm sure that I won't be opening the door to some new undocumented workers. Even the feral cats will continue to be begrudgingly put up with, at least until I'm sure that all of the rats are toast...but that never really happens.
In the end my new coop has already evolved from a nature friendly open topped pen to a veritable Ft. Knox of poultry prophylactics. Concrete, insulated masonry, buried plaster lath, broken glass and wire have replaced the original idea of some pine boards and chicken wire. Thanks principally to what I've learned from others here we're gradually adding more and more ideas to our castle keep in order to attempt raising domesticated birds in the midst of our wildlife preserve. It really gives one a much greater appreciation of what the early pioneers had to endure. At least if we loose a bird we can still run to the store for some eggs and order some new chicks with a few clicks of a mouse.
