The managed feral cat colony has been evaluated extensively. There are numerous comprehensive, genuinely objective studies, conducted by parties with the resources and time to accommodate the broad scope and depth a thorough study requires. Usually, these parties are universities, like Cornell, or governmental agencies the nature of which is agriculture, animals or the environment. San Diego and Santa Clara Counties have studied the issue, as has the city of Berkeley, CA. I mention them because California and Florida are comparable much more than not.
Although persons long have held feral cats responsible for serious threats to and deaths of songbirds and scarce or rare bird species, no direct evidence supports this and much evidence contravenes it. Importantly, a distinction must be made between untended, independent feral cats and a properly managed feral cat colony. The differences between the two are great. For instance, in Rome, Italy, the Coliseum is home to multiple managed feral cat colonies. The total number of colony cats exceeds 250. This programme is endorsed by the Italian government, which, based on the evidence, does not regard the cats as menaces to birds or to the environment. If the Italian government thought otherwise, it would eliminate the colonies by eradicating the cats.
Contrary to the popular perception, cats are not particularly good hunters of birds. Birds are highly sensitive to their surroundings, scattering immediately at the slightest sense of any danger. Where I live, I witness this on an almost daily basis. I maintain bird feeders in our yard, which also is routinely and frequently visited by at least quasi-feral neighbourhood cats.
For one thing, and why it is overlooked baffles me, birds can fly away whereas cats can not fly at all. I have seen a cat patiently stalk the birds at a feeder. Usually, the birds take flight before the cat even lunges. When a cat does lunge towards a given bird, though, the cat fails to catch the bird. Exceptions are negligible. In almost 15 years here in North Florida, and in over 25 years in Hollywood, I doubt I have seen the telltale remnant bird feathers more than a dozen times. Of those times when a cat did indeed kill a bird, the bird invariably was a pigeon or a dove, as you will. The difference between pigeons and doves is slight; both feed on the ground, making them the birds most susceptible to being caught by cats. These are not songbirds.
Certain birds, like mockingbirds and blue jays, have taught more than one cat a memorable lesson about the prudence of hunting birds. These exceptionally territorial birds successfully defend each other, their nests and particularly their young from attack.
Cats have an inherent aversion to heights. I have seen quite a few cats go up trees to catch birds. The typical scenario I have witnessed is the bird flies away long before the cat comes near to approaching it, then the cat remains rather high in the tree, afraid to climb down. I reluctantly have scaled trees to help cats make a safe return to the ground. Now 58, this is not something I feel comfortable continuing to do. Cats also dislike going into the water, making the few bird species common at beaches, like sandpipers, safe for all intents and purposes from successful cat attacks.
Indeed, the birds regarded as being in danger of cats, such as cardinals, sparrows and orioles, are in greater danger of other birds – raptors, or birds of prey. I have witnessed many successful attacks of small birds by raptors. Again, being birds, raptors, unlike cats, can fly, negating the crucial defence of the smaller birds upon whom they prey.
The barnyard or farm cat, the famed mouser, never has been regarded by the farmer as an hen-house threat, notwithstanding hens, roosters and chickens being birds.
The staple diet of non-colonised feral cats is mammals. This is followed by small reptiles and only after that by birds, which never constitute more and typically constitute much less than about 20% of a non-colonised feral cat’s meagre diet. That feral cats are not proficient hunters is shown by their relatively emaciated appearance. Efficient bird hunters are not undernourished. Scavenging is easier than hunting and humans’ wasteful habits facilitate this practise. Non-colonised feral cats are anything but robust animals. This problem is rectified by the managed colony, to the betterment both of cat and of bird.
By far the greatest threat to birds is humans. Pesticides, habitat depletion, adverse environment treatment, e.g., pollution, and other human-caused factors dwarf any hazards any birds face from any cats. (This hardly applies only to birds.)
In a managed feral cat colony, the cats are sterilised, provided with food and given at least fundamental, basic or rudimentary veterinary care. The system works. In humane terms, it is the least humans can do for a problem humans and humans alone created. Economically, it is vastly cheaper than continuing to round up and process highly reproductive feral cats, the population of which increases geometrically in the absence of sterilisation. Moreover, the resultant void or vacuum from colony evacuation induces an influx of other feral cats, perpetuating the problem. Competent colony management is a true solution.