Cats vs. birds: Who has to die?

A controversial bill that would allow people to trap, sterilize feral cats, then release them where they were trapped is wending its way through the Virginia state senate, and it's had the unintended consequence of dividing the animal lover community between the save-the-cats and save-the-birds crowd.

Kayla Christiano, of cat advocacy group Alley Cat Allies, argued the case for the trap-neuter-return (TNR) protocol, accompanied by a stray cat dubbed "Patches," who's about to head home to his suburban Maryland neighborhood. "He was brought to the clinic where he was neutered, he received his vaccination for rabies, and the top of this left ear was clipped so we know that that cat has been sterilized and vaccinated," she said in an interview with CBS News.

Under the program, the cats released also have caregivers, who feed them and check in on their health. Those on the side of the feral cat say that TNR is the most effective approach to stabilizing and reducing cat populations, while at the same time saving them from kill shelters, which take in the cats, then euthanize them.

But as far as bird advocates are concerned, what's good for the cats is bad for the birds. All of those cats are killing birds by the billions each year - an estimated 1.4 to 3.7 billion in the U.S., according to the journal Nature Communications. And a University of Nebraska study published in 2010 says feral cats are responsible for killing off 33 species of birds worldwide.

Grant Sizemore, the director of the Invasive Species Program at the American Bird Conservancy, says that the cats need to be better controlled. "They contribute to widespread ecological degradation, including the predation of wildlife, and a number of health concerns," he told CBS News.

Cat-lovers counter that neutering and returning cats is an effective way to reduce and stabilize their population. Sizemore, on the other hand, favors "removing these cats from our local neighborhoods and parks and then returning them to the shelter where they have the chance of finding a forever home."

And Sizemore himself has adopted a feral kitten. But many stray cats are not suitable for adoption, so, "really, the only alternative to TNR is to bring them to the shelter where they are killed," Christiano said.

Sizemore says that's to be expected. "Some of the cats will need to be euthanized if they cannot find a home. Unfortunately we have a major pet over-population."

Further, cat advocates, he says, are wrong when they claim that TNR reduces cat populations. "On the contrary, sometimes it leads to increases in the number of cats in the environment, because people see these feral cat colonies as a convenient place to abandon or dump their pets."

PETA sides with the bird lovers, although its reasoning has more to do with its evaluation of the TNR program. Although it reluctantly supports TNR under very specific circumstances, PETA's statement notes "countless reports" in which cats "suffer and die horrible deaths because they must fend for themselves outdoors," and it asserts, "Having witnessed firsthand the gruesome things that can happen to feral cats, we cannot in good conscience advocate trapping and releasing as a humane way to deal with overpopulation."