JONES BEACH STATE PARK, N.Y. — On a brisk day in early spring, the scene at Jones Beach was quiet.

Besides a few fishermen checking to see if flounder or ling were running, there were just the piping plovers, newly arrived from their wintering grounds in the Bahamas, looking for nesting spots, and the cats, about 30 of them, living in makeshift structures of cinder block covered with tarps.

The stillness belied a simmering conflict, though, whose roots are as ancient as the antipathy of feline and avian: a battle between cat people and bird people over whether the two species should coexist at Jones Beach.

Bird lovers and conservationists say the cats here threaten the nesting plovers — small, sand-colored shorebirds, listed as endangered by New York State — that lay their eggs in shallow depressions on the open beach. The American Bird Conservancy, a nonprofit that supports protecting birds and their habitats, is urging the state to get rid of the cats. But cat rescuers who for years have cared for the colony say they deserve to stay.