Looks like it’s a bad time to be a seabird.
According to a recent study out of the University of British Columbia, monitored seabird populations around the world have declined 70 percent since the 1950s, an indication that there could be something seriously wrong with marine ecosystems.
“Seabirds are particularly good indicators of the health of marine ecosystems,” Michelle Paleczny, a UBC master’s student and co-author of the study, said in a press statement. “When we see this magnitude of seabird decline, we can see there is something wrong with marine ecosystems. It gives us an idea of the overall impact we’re having.”
The study linked the decline in seabird populations to a slew of factors, including over-fishing — which caused a decline in the fish the birds rely on for food — and ecological and environmental changes caused by climate change. The researchers also point to the introduction of invasive predators, plastic and oil pollution, and dangerous fishing gear as potential causes for the decline. All told, the study found that seabird populations globally have declined by 69.6 percent in the last 60 years, representing a loss of some 230 million birds.
Seabirds tend to travel long distances foraging for food, but often return to the same colonies to breed. A change in colony populations can be an indication that coastal and marine ecosystems might be off — but a drop in colony populations also can have a negative impact on the ecosystems, as seabirds eat (and are eaten) by a variety of species, and help fertilize food webs with their waste.
“Our work demonstrates the strong need for increased seabird conservation effort internationally,” Paleczny said. “Loss of seabirds causes a variety of impacts in coastal and marine ecosystems.”
The study comes just days after the U.S. Fish and Wildlife Service raised concern over the disappearance of tens of thousands of nesting birds from a 150-acre Florida island refuge.
Vic Doig, biologist for the U.S. Fish and Wildlife Service, told Reuters that the birds, which have been coming to Seahorse Key on Florida’s Gulf Coast for over 100 years, returned to the island in April only to disappear in May, leaving behind thousands of unhatched eggs.
Rare bird species like snowy egrets and tri-colored herons are among the missing birds — at times, more than 10,000 to 20,000 nesting pairs have been known to call the island home.
“When the birds are nesting there, the island is a chaotic, loud, busy place,” Doig said. “All of a sudden, it’s like a ghost town.”
Bird colonies have been known to abandon their nests in the past, but the scale and diversity of this particular case has wildlife experts mystified.
“We’ve seen a lot of abandonments in the Everglades and in some seabird colonies, but there’s never been such synchronicity involving so many species at once,” Peter Frederick, a wildlife biologist at the University of Florida, told TakePart. “Nothing seems to fit together.”
Wildlife officials don’t know what caused the birds to leave the island. They haven’t found any signs of traumatic injuries or disease, and say it would be unusual for a predator to successfully scare off so many birds over such a large area.
It’s possible, officials say, that the birds could have been spooked by an airplane, drone, or helicopter. In recent years, nighttime flights over the area have increased, and a helicopter ferry was recently put in place to take visitors to a nearby island. But the idea that such noise could be disruptive enough to cause such a large-scale abandonment, Doig said, is a long shot.
Without any substantial leads, Doig told Reuters that officials will simply have to wait and see if the birds return next year.
Regardless of what made the birds in Florida disappear, birds in general are expected to face major challenges in the coming years. According to a 2014 report released by the Audubon society, about 21 percent of North America’s bird species are at risk of losing more than half or all of their habitat by 2050 due to climate change, and nearly half of all species are threatened by climate change to some extent. And the National Wildlife Federation has warned that climate change will likely cause a mismatch between bird migrations and the ecosystems they depend on for food and shelter, as earlier springs could cause migratory birds to take off before the food sources they depend on become available.