Beyond The Nest

May 06, 2005

The Ocean Conservancy
By William H. Woodwell

A strange thing happened last summer on Machias Seal Island. Located about 10 miles off the coast of Maine on the U.S.-Canada border, this 15-acre rocky outpost plays host each year to thousands of nesting seabirds, including Arctic and common terns, Atlantic puffins, razorbills, and more. But in 2004, researchers from the University of New Brunswick reported that not a single tern chick on the island survived the summer nesting season—this on an island that boasts the largest tern colony in the Gulf of Maine. The reason for the die-off: starvation.

The researchers, who live on the island all summer to monitor the seabird population, also noticed that terns and other birds were feeding their young large amounts of tiny larval fish. The birds’ preferred food is juvenile herring. Some adult terns were even seen bringing moths and ants to the nests—anything to keep their chicks alive. The situation shocked seabird experts.

“It really made people stand up and take notice,” said Linda Welch, a biologist with the Petit Manan Wildlife Refuge, which includes more than 46 offshore islands in Maine. “We take for granted that these birds will have enough food to survive.”

The lack of food in 2004 has been blamed on everything from apparent declines in some fish populations to poor weather and changing ocean temperatures. Regardless of what caused it, however, the death of the tern chicks shows how dependent Maine’s seabirds are on the health of the ocean environment—and how protecting these birds is about much more than guarding the rocky islands where they raise their young.

A Short History of Maine’s Seabirds Maine’s 3,500 coastal islands have long provided a safe haven for seabirds. The islands are a choice habitat because of the lack of mammalian predators, the presence of few avian predators, and the cold surrounding waters, which hold an abundance of fish.

But with the arrival of European settlers in the 1600s came new challenges for the seabirds. People began hunting them and collecting their eggs, while livestock trampled their nests and habitats. But these early threats were nothing compared to the havoc wreaked by people’s desire for a pretty hat.

In the late 1800s, Maine’s seabirds—particularly terns, herons and egrets—became prized for their feathers, which provided a fashionable adornment for the growing millinery trade. Combined with the increasing use of birds for fish and lobster bait, the feather hunt resulted in steep population declines.

“The turn of the century was the low point for these birds,” said Stewart I. Fefer of the U.S. Fish and Wildlife Service. “After being hunted for bait and feathers, they were truly on the verge of extinction.”

The numbers began to recover with enactment of the Migratory Bird Treaty Act in 1918, which set out to protect the birds, their nests and eggs from human predation. Pressure on the birds also let up as people began to leave the islands for the mainland because fewer could support their families fishing. Common and Arctic tern populations rebounded, reaching a high of almost 16,000 pairs along the Maine coast in 1940.

But the recovery was short-lived. During the mid-1900s, open landfills along the coast and an increase in fishery waste provided easy pickings for gulls. The gulls began competing with terns and other seabirds for prime habitat while preying on tern chicks and eggs. “Unfortunately for terns and other seabirds, gulls are very efficient predators,” explained Welch.

By 1977, the tern population in the Gulf of Maine had declined again—to roughly 5,000 nesting pairs. Since then, conservation groups, government agencies, and concerned citizens have been working to restore and protect the seabirds’ island habitats—chiefly by acquiring important nesting islands, keeping gulls away, and reintroducing puffins and other species to the islands.

Protecting the Food Source

As the events on Machias Seal Island in 2004 showed, protecting the seabirds’ food source may be critical. “We protect their nesting sites,” said Fefer. “But the birds won’t be there if they don’t have any food.”

Dr. Stephen Kress, Director of the National Audubon Society’s Seabird Restoration Program, and the U.S. Fish and Wildlife Service are working with observers on seven Gulf of Maine islands to study seabird diets. So far, researchers have learned a lot about connections between fish stocks and bird populations. Kress noted that just a few key species of fish, including white hake and Atlantic herring, support all of the seabird populations in Maine. “These birds are extremely vulnerable to what happens to the fish.”

Kress added that fish stocks vary from year to year and that it is hard to pin food shortages on any one cause. However, many people in Maine have expressed concern about industrial fishing practices such as “midwater trawling,” which has been reported to cause localized depletions of herring in nearshore waters.

According to Susan Farady of The Ocean Conservancy’s New England office, commercial fishery management plans do not fully consider the importance of herring and other species as prey for other animals. “We need to examine how fishing affects the broader ecosystem,” she said.

Moving Toward an Ecosystem Focus

Adopting an ecosystem perspective also would direct more attention to the impact of pollution and contaminants on Maine’s seabirds. Rebecca Harris, Program Coordinator for the Seabird Ecological Assessment Network, or SEANET, noted that Machias Seal Island is not the only place in the Gulf of Maine where seabirds have been facing new challenges of late.

Over the past three summers, tern chicks on Stratton Island in southern Maine have exhibited strange symptoms of disease, including lethargy and rotting legs; large numbers have died. The same symptoms have shown up in chicks on Pond Island near Bath, Maine.

Harris said it is still unclear what might be causing the problem, but man-made contaminants are an obvious suspect. Over the years, studies have shown high levels of polychlorinated biphenyls (PCBs), dioxin, mercury, and other contaminants in fish and wildlife throughout the Gulf of Maine. “We need to view seabirds as indicators of the larger ecosystem and of what is going on with contaminants, harmful algal blooms, declining fish stocks, and disease, all of which have the potential to contribute to large-scale mortality in these birds,” said Harris. Oil pollution is another threat—not just large spills, but also the more insidious effects of what Harris refers to as “chronic oiling.” Boaters illegally dumping oily bilge waste is an example.

Debating the Solutions

The release of the Pew Oceans Commission and the U.S. Commission on Ocean Policy reports in 2004 drew attention to the need for an ecosystem-based approach to ocean management. Such an approach would pay off for seabirds in the Gulf of Maine, according to Susan Farady.

“These birds need their islands, but they also depend on the sea,” she said. “This is a great example of the challenges of ecosystem-based management—adjusting our approach to reflect the interdependence of species in the ocean ecosystem.” One solution would be to create marine protected areas to protect seabird food sources and the islands where they nest. Fishing and other activities that are disruptive to the birds would be limited in the affected waters. Research can help scientists discover how protected areas can help seabird populations by clarifying the connections between fish stocks and seabirds and by exploring the problems posed by toxic pollution and other threats.

According to Kress, more research would help scientists determine exactly how far seabirds travel to get their food. But some experts say we already know enough to be smarter about managing ocean resources to protect seabirds and other species. “There are all these obvious connections between species and the health of the ocean and the health of all the animals that depend on it for their survival,” said Harris. “It’s just common sense to look at the bigger ecosystem and how it’s affected.”