Researchers with the Florida Fish and Wildlife Conservation Commission have received reports of more than 150 dead or distressed greater shearwaters, gull-like birds, along Florida's east coast this week. After examining some of the birds, researchers believe these deaths are related to stress from the species' long, trans-Atlantic migration.
Greater shearwaters migrate from their primary breeding grounds in Tristan da Cunha, a group of islands off the southwest coast of Africa, across the Atlantic to Canada, according to the Peterson Field Guide for Eastern Birds.
"This long migration, coupled with storms and high winds, can take its toll on some immature and older shearwaters, sapping their strength and making it difficult to feed," said Dan Wolf, an FWC research biologist, in a news release. "Upon examination of some of the dead greater shearwaters this week, we found the birds were young and emaciated, consistent with normal migration mortality."
Because greater shearwaters live most of their lives on the open sea, the deaths are only seen alongshore when winds are blowing inshore, the FWC stated.
Local wildlife rehabilitation centers have received dozens of dying great shearwater birds in the past two weeks.
Since June 16, the Treasure Coast Wildlife Center in Palm City has received about 20 birds and none have survived, said the center's executive director Dan Martinelli.
"They're literally on death's door. They are emaciated," said Martinelli who added most of the recovered birds are juveniles and older adults — usually the weakest of the flock. "It's a major event. I think we can characterize it as a mass die-off."
According to Smithsonian Marine Station fellow Sea McKeon, who holds a Ph.D. in zoology from the University of Florida, sometimes Mother Nature isn't the most nurturing force.
"We've had tremendous rain and wind blowing over the ocean," said McKeon, who added the inability to hunt stemming from exhaustion might be causing the birds' demise. "The wind has pushed them onto our beaches. Once they're on land, they are completely helpless."
The seabirds have dark plumage, a dark cap and a wing span of 3 feet. The shearwater is one of only a few bird species to migrate from breeding grounds in the Southern Hemisphere to the Northern Hemisphere, the normal pattern being the other way around. The seabirds feed on small fish pushed to the ocean surface by tuna and dolphin during their annual summer migration along the Gulf Stream to Canada, McKeon said.
On Thursday morning, McKeon found four dead shearwater birds on North Hutchinson Island in Fort Pierce. He estimates hundreds have been washing up on beaches from Cape Canaveral to Miami.Animal experts at Creature Safe Place in Fort Pierce reported in the past two weeks they received about 10 shearwaters clinging to life. Executive director Winnie Burns said despite attempts to hydrate the birds, none survived.
"This is not a common occurrence," Burns said. "We usually get two a year."
Martinelli plans to ship 10 of the dead birds early next week to FWC in Gainesville for testing.
"This is a sad event, but it is probably a natural event," said Martinelli.
FWC states that migration-related deaths of greater shearwaters occur every year around this time, though the number varies. In 2007, researchers received reports of about 1,000 dead shearwaters during the migratory season.
To report dead birds
The public can report dead birds to the Florida Fish and Wildlife Conservation Commission online at MyFWC.com/Bird. Anyone who encounters a dead or distressed bird is asked not to handle it. For assistance with sick or injured birds, citizens should contact a local wildlife rehabilitative facility.
How to handle a stranded shearwater bird
Loosely wrap the bird in a towel by lightly dropping the towel over the bird
For transport, put the bird (still covered in the towel) in a cardboard box, recycle bin or empty cooler. Make sure to keep the towel over the bird's eyes to keep it calm
Do not feed the bird or give it any water or attempt to put it back in the water
Take the bird to the nearest wildlife rescue facility.
Sources: Florida Fish & Wildlife; area wildlife rescue facilities