HULA VALLEY, Israel — The sound is low and throaty — a crow's call crossed with a sea lion's bark. Silvery-black wings flap impatiently, and webbed feet stamp up and down. In a two-tiered wire enclosure in Israel's Hula Valley, a dozen trained cormorants are getting ready to have their eating habits recorded on video.

"Ready?" Tamir Strod, a graduate biology student at the Technion-Israel Institute of Technology (Israel's version of MIT) pulls a lever to open a wire door. Quick as a flash, a cormorant dives through the door into a series of mesh tunnels, where it finds a pickled St. Peter's fish and gulps it down whole.

A snack here, a snack there — these birds are certainly not suffering for science. But their mission is critical. They're representing thousands of birds who migrate annually through Israel, and whose lives are being endangered by increased levels of agriculture in the Hula Valley, in Israel's northern Galilee region.

"Local fishermen shoot to kill," says supervising Professor Zeev Arad. "They complain that the birds are pests — but they don't distinguish between birds, so they're killing off members of endangered species."

It's a problem Arad and his team of Technion graduate students have taken to heart. Approximately 20,000 birds — herons, cormorants, ibises, pelicans — migrate annually through Israel. Some, like the pygmy cormorant, are on the verge of global extinction. "We're talking here about natural treasures," Arad says

As with many environmental issues, though, it's hard to make governments and industries care. That's where Arad and his students come in. By analyzing the birds' habits and eating patterns, they hope to convince fishermen that coexistence with their winged neighbors is possible. In many ways, it's a typical Israeli story.

Ironically, the birds' current behavior patterns were shaped by the farmers themselves. In the 1950s, the Hula Valley's swamps were drained to produce more agricultural land for Israel. It was a misjudged project: much of the recovered land proved infertile, and re-aquification projects are now under way. In the meantime, migrating birds have been obliged to forage from fisheries in the area.

Arad, who has been studying the birds onsite for the last three years, has found that they are highly adaptable. Many, for example, have changed from day to night feeding in order to avoid the fishermen's guns. Unfortunately, this is equally dangerous for the birds — with limited night vision, many fly into power lines and get electrocuted.

"We've picked up hundreds of carcasses from the ground," says Arad. As part of their research effort, he and his team dissected the corpses and analyzed the birds' fat reserves to determine exactly how much food they need in order to make the journey to Africa.

In another experiment, Arad convinced local chicken farmers to donate chicken corpses for the migrating birds to feed on. "They adapted very easily to the alternative food source — and later, when we offered them a choice of chicken or fish, they chose chicken," he says. In Arad's view, their eclectic appetite proves that the birds need not be a threat to the fisheries.

Other feeding experiments show that the birds might actually be helping fish production rather than hindering it. "We've found that they might be serving as sanitary agents, feeding on weak and dead fish," Arad says.

Passionately discussing his work, Arad tells of how he once equipped a pelican with a satellite collar, tracking its progress southward — only to have Sudan complain to the U.N. that Israel was spying on it "with a satellite carried by a bird."

Strod, too, has become deeply involved with the cormorants in his charge. "I'm the birds' father and mother," he admits with a smile. "It's hard sometimes. I can't leave for long. If I'm away for more than two days in a row, I need an assistant to come in and feed them."

Opening the door to the wire enclosure, Strod calls his special pet — a pygmy cormorant with two broken wings. "He arrived at the center with a sock over his head, so we called him Socks," Strod says. The bird hops out into a small kitchen area, where Strod tosses him fish from a small freezer.

Arad and Strod hope their data will eventually convince local agribusinesses to go easy on the winged visitors. In the meantime, in addition to parenting a dozen cormorants, Strod spends time listening to fishermen's stories about the birds.

"The fishermen help me a lot," he says. But he adds, "when we have the results of the tests, we'll be able to talk about real things — like how they're going to treat the cormorants."

And with that, Socks, who looks more than pleased to have done his part, hops back into the enclosure.