There are two sides to this story(rant?). Most "feral" cats and dogs are actually someone's pets-- granted, in many cases this is a loose term. The dogs are animals that are kept around for "protection" and as such allowed to run free without much monitoring. Being pack animals they can form groups of two or more that become a danger to other animals, especially domestic stock, in particular young and those that cannot escape them. Often too the owners do not realize their animals are a problem (or care). We've had instances where standard poodles and boxers were causing problems when the owners thought they were just outside taking care of business. I've had hunting dogs--both hound and retriever types--show up here that had simply gotten lost while out with their owners on hunting trips--all had collars and licenses and were captured and returned. That being said, probably 99% of the dog damage done to poultry has been done by either the flock owner's dog or a neighbor's pet--not feral dogs.
As far as feral cats are concerned most, at least in the rural area where I live, are farm cats. These are cats that farmers keep around for the specific purpose of keeping rats and mice down around their barns and outbuildings. Most, but certainly not all, are fairly well cared for, after a fashion--some farmers make sure they are vaccinated, a few even spay the females and feed them. Sorry to say some of the populations are supplemented by dropped off pets. Yes these cats wander a bit and yes they do take songbirds--especially young ones--as well as baby rabbits, chipmunks, and other mammals. In some urban areas cats may be the only predators on these populations. Most, probably 99%, don't threaten domestic poultry, specifically full grown chickens, and even those that do probably cause less problems than hawks, coons. skunks, possums and weasels combined. Certainly they are no where near the problem dogs are. Additionally, in areas such as where I live, the life of any feral cat that wanders too far is very short given the number of coyotes that prey on them.
BTW as a disclaimer, I have had, over the years, a number of indoor/outdoor cats (currently 3, all over 12 years old, that fit that category) most have/will bring home anything they catch to show it off before eating it. Usually their prey is a mammal of some type--rabbit, squirrel, chipmunk, mouse, rat or vole--rarely do they take a bird in spite of the fact we have a feeder right by the house. As I've said before I've found more dead songbirds that have died from smacking into the house windows than all our cats have ever killed.
Finally (and this will probably get me in trouble) there are a few people that post here that seem to think that, because they have chickens this gives them the divine right to kill anything that could possibly be a threat to them. I live well outside town in a fairly wooded area and have, in my 25+ years of keeping chickens lost a few of them to foxes, hawks, coons, skunks, possums, weasels and dogs(mostly dogs) but I also see all of the above plus coyotes and cats around all the time. They aren't all bothering my birds either because they don't need to or can't get at them. If you want to protect your birds, instead of killing anything that could be a threat, how about protecting you flock and learning to live with possible predators? Realize that you cannot exterminate all the predators--there are always others just wait to take their place--so learn to live with them.