In the world of bird hierarchy, crows are considered one of the most intelligent birds out there. And it's this intelligence that has Cape Cod National Seashore officials considering a plan to kill some of the smartest crows on the cape with hopes of bolstering populations of piping plovers, a diminutive bird that, while perhaps not as brainy as crows, could face extinction if its numbers don't increase.
The problem, you see, is that some crows on the cape have developed a taste for plover, and they exploit this taste during the nesting season. While seashore biologists try to protect nesting plovers by placing exclosures -- a wire cage that has squares large enough for plovers to pass through but not crows -- around nests, some crows have figured out that they can get around this by landing with force atop the exclosure.
"Crows and other predators learn that ... a hard landing on top of the wire box might be enough to cause the parent plovers to get excited and move out of the cage, and then once they do that they’re fair game," says seashore Superintendent George Price. “Once you get the adult, who can no longer take care of the egg, on a hot summer day the egg gets cooked very quickly.”
With hopes of ending this behavior, at least in the short term, seashore biologists and U.S. Department of Agriculture specialists are proposing to poison crows that exhibit this particular hunting knowledge during the March-May nesting season. To do that, they would set up topless exclosures, which some crows have come to associate with nesting plovers, and plant eggs laced with DRC-1339, a "slow-acting avicide registered for controlling blackbirds, starlings, pigeons, gulls, magpies and ravens that damage agricultural crops, personal property or prey upon federally-designated threatened or endangered species." The poison is expected to kill crows that ingest it within 12-72 hours.
To explain this approach to the public, Superintendent Price plans to host two opening houses -- one this Thursday at the Salt Pond Visitor Center in Eastham, Massachusetts, at 5:30 p.m., and one on March 3 at the Provincetown Center for Coastal Studies, also at 5:30 p.m.
Piping plovers get a hierarchical edge over crows on the national seashore because they are listed under the Endangered Species Act as a threatened species along the Atlantic Seaboard, and an endangered species along the Great Lakes. Crows, while smart, are plentiful and, therefore, seemingly expendable. And, the national seashore seems to be pretty good habitat for plovers. While Cape Lookhout National Seashore reported only 37 nesting plovers last year, and Cape Hatteras National Seashore just nine, at Cape Cod National Seashore the number was closer to 90.
"What brought us to this point now is that, basically, we have plateaued in our success rate with our productivity for the piping plovers," said Superintendent Price "We’ve had a tremendous boom in nesting pairs. Back in the 1980s there were only about 19 nesting pairs, and now we’re anywhere between 70 and 90 nesting pairs, depending on the year."
With hopes of moving beyond the plateau, seashore officials focus on restricting visitor access when plovers are nesting, manage off-road vehicles on the beaches as much as possible, and work to thwart predators.
"Last year, for instance, we had a phenomenon where a full one-half of one of our most popular beaches had to be roped off for the entire season because of nesting plovers and terns," said Superintendent Price. "Marconi Beach. That’s a beach where we would normally get between 10,000 and 13,000 visitors a week during the summer, so you can imagine the impact when a full half of it is roped off. So this is an overall approach to try to achieve some more flexible management and to be able to continue our success with the plovers, both with the nesting pairs and with the productivity rates.”
Predation by crows is blamed for the loss of roughly one-third of plover eggs each year, and they also are thought to prey on chicks and small adults. Still, not everyone is thrilled with the poisoning plan. According to a story in the Cape Cod Times, some crow supporters might attend the meetings in black feathered costumes. And others are suggesting that the seashore lace the bait eggs with something that wouldn't kill the crows but make them sick enough -- something akin to an avian antabuse-- that they'd think twice about another course of plover.
Superintendent Price believes some of the opposition stems from a 1990s' effort by the U.S. Fish and Wildlife Service to kill seagulls to benefit other nesting shorebirds on the Monomoy Wildlife Refuge that lies just south of the national seashore.
"They ended up with this legacy situation where they had seagulls literally dropping out of the sky onto people’s lawns and in their pools and in their picnics, and it really generated an awful lot of excitement, as you can imagine," said the superintendent. "So as far as a very public process where this is discussed, most people harken back to that example. So they’re assuming that somehow the federal government didn’t learn its lesson and that this is going to be a redo of that exercise."
However, Superintendent Price explained, the poisons will only be set out on the seashore when crows exhibit this particular hunting behavior, and this year will be used only along the Duck Harbor and Bound Brook beaches as a pilot project.
"If there aren’t crows in the area, and they don’t seem to be bothering the nests, then we’re not going to activate the USDA process," said the superintendent.