Wildlife advocates are scratching their heads over the discovery of an unusual number of sick terns in the region.
Nearly 20 emaciated and dehydrated juvenile terns have been brought to Wild Care in Eastham over the past few weeks, found in towns from Chatham to Provincetown. Most have died; three remain in the care of the wildlife rehabilitation facility, according to Executive Director Stephanie Ellis. The majority of the ill birds were common terns, but at least one was an endangered roseate tern, she said.
“A couple of hundred” dead common terns were found last week in the tern colony on South Monomoy Island, said Eileen McGourty, acting refuge manager and biologist at the Monomoy National Wildlife Refuge. Most were this year's hatchlings.
“That's unusual,” she said. “We don't usually have that much mortality in the colony.” The island hosts the largest tern nesting colony on the Atlantic seaboard, with more than 13,000 pairs rearing young every summer. An initial report on one carcass sent to the National Wildlife Health Center in Madison, Wisc., only indicated that the bird was emaciated and dehydrated. She said five more dead birds were being sent to the facility this week for further testing.
McGourty said said the refuge has received reports from beaches around town of terns floating in the waves and surf and crawling on the sand near beachgoers. “It's unusual behavior for the birds to be that close to people,” she said. Most appear to be juveniles and look sickly, lethargic and sometimes with droopy wings.
It's not unusual to see emaciated birds at this time of year, Ellis said. Usually Wild Care receives about a half dozen, “but these numbers are alarming.”
Since July 21, Wild Care received 20 terns, “mostly juveniles. They all come in emaciated, really weak,” Ellis said. Many have drooping wings and were found in close proximity to people. One was found under a car at a Wellfleet parking lot. At least one was an adult tern, from the Monomoy refuge, that appeared to be suffering from the same malady as the younger birds. Some had other injuries. Most died; three common terns are currently being rehabilitated at Wild Care's Eastham facility.
The juvenile roseate tern was found at Jeremy's Point in Wellfleet, suffering from the same symptoms. “He was in terrible shape,” Ellis said. Because of its status as a state and federally endangered species, Wild Care obtained permission to treat the bird from the Massachusetts Division of Fisheries and Wildlife. The bird was given oxygen and fluids but did not survive.
“It seems very much like an Outer Cape event,” Ellis said, noting that most of the terns were found along the Atlantic and along the Cape Cod Bay shore on the Outer Cape. One was found on Long Pond in Brewster. Wild Care is planning to send the carcasses to the state for analysis “so we can get some answers,” she said. She speculated that warmer waters may have changed the distribution of the birds' food source, which is primarily sand lance, small bait fish, crustaceans and insects.
Unlike past years, the Monomoy tern colony is not being monitored 24 hours a day due to the pandemic. McGourty said the numbers in the colony appear to be similar to last year. Last week's visit didn't cover the entire colony, but even discounting the dead birds that were obviously killed through predation, there were still an unusually number of dead juvenile terns.
“We don't know what's happening,” McGourty said. “There's a lot of speculation,” including food availability and disease, but until there is further analysis of the dead terns, it's impossible to say if there is a specific cause to the die-off.
“At this point we have more questions than answers,” she said.