Inquirer: Sandy leaves pantry bare for N.J.’s coastal raptors
By Sandy Bauers, Inquirer staff writer
Saturday, February 9, 2013
Amid all the destruction and havoc along the Atlantic Coast during Hurricane Sandy, quiet carnage was taking place in South Jersey’s marshes.
Few noticed. Fewer still, in all likelihood, cared. But in birding circles, the ramifications have been huge.
As the storm surge rose, the waters flooded the underground burrows of two signature marsh species – tiny furry things, the meadow vole and rice rat.
Naturalists later found an astonishing number of their little corpses in the high-water “wrack line” of marsh grasses and other detritus left by the storm.
And now, birders throughout South Jersey are seeing the upshot: a scarcity of northern harriers, red-tailed hawks, and other raptors that depend on a quantity of rats and voles for winter food.
“This is the worst year for birds of prey on the bay shore that I’ve seen in 36 years,” said Pete Dunne, director of New Jersey Audubon’s Cape May Bird Observatory. “The impact is dramatic.”
Clay Sutton, who for more than 25 winters has been conducting bird counts on South Jersey’s Maurice River, is seeing the same thing.
And now, the numbers are in from a midwinter count of 15 salt marsh sites.
Harriers – birds most intimately linked to the salt marsh – have numbered up to 135 in recent years, based on brief scans of the marsh just before and after sunset.
This year, the count is just 63 so far, not expected to top 75 once the final two site reports are in, said Tom Reed, a bay shore birder who is heading the effort.
Eagles, which eat fish and carrion, were not affected – good news for anyone planning to attend the daylong Cumberland County winter eagle festival Saturday at the fire hall in Mauricetown.
The effect on other raptors was predictable, Dunne said. He walked the marshes after Sandy and, noting the tiny rodent bodies, knew it would be a hard year for the birds.
Brian Johnson, manager for the Natural Lands Trust’s Glades Wildlife Refuge in Cumberland County, saw the same thing when he cleared trails after the storm. With each turn of the pitchfork, he saw them – about 100 dead rodents along a 200- to 300-foot stretch of marsh trail.
Rice rats are known to be good swimmers, but conditions in Sandy were extreme, he said. “The water came up and the waves were so large” that the tiny animals couldn’t cope.
Something similar happened after Irene in 2011, but since that storm came in August, the rodents had time to repopulate somewhat, Dunne surmises. Higher tides like the ones forecast for this weekend are not usually a problem, Johnson said. “They’ll just swim to higher ground.”
Even in the case of Sandy, no one thinks this is either a rodent or an ornithological Armageddon. With the dinner table bare, the birds simply moved on. They’ll return when rodent populations recover.
Which could happen quickly.
Rice rats can have about six litters – up to five pups each – every year, said Kent Edmonds of Indiana University Southeast. He sloshed around Delaware’s salt marshes while earning his doctorate – and his lifelong passion for rice rats – at the University of Delaware.
Researchers know that meadow voles are impressively fecund as well. They are sexually mature when they are 20 days old. Gestation is less than a month, and the litter can be up to 11 pups.
Nonetheless, “the wild is a dangerous place,” Edmonds said. “They’re going to have to find mates and avoid predators. If they can do all that, then, yeah, they may be able to have a significant year.”
To a philosophical Dunne, this is all part of normal cycles, “a dramatic and poignant example of how dynamic the natural world is.”
“Birds and rodents and tides have been working this out for thousands of years,” he said.
This time, the tides won.