June 19, 2013
Seabirds Warn of Ocean Change
What can 30 years of research and monitoring on Maine seabirds teach us? That the marine environment is changing fast. That ocean birds may be failing to adapt. That the scope of few marine threats – from ocean warming and offshore energy development to competition from commercial fisheries − could have been foreseen when Maine Coastal Islands National Wildlife Refuge staff began studying the birds in the early ‘80s.
The refuge, made up of more than 50 islands in the Gulf of Maine, uses data from research and monitoring to manage Maine seabird colonies and try to stem the birds’ decline.
Consider the Arctic tern. Its 36,000-plus mile-per-year migration from its wintering grounds in Antarctica to its Maine breeding grounds is the world’s longest; the little bird makes the equivalent of three round trips to the moon in its 30-year lifetime. Small light-sensing units called geolocators have been used to document the distance flown. But over the last five years, counts of Arctic terns in Maine have dropped by 42 percent, from 4,224 pairs in 2008 to 2,467 pairs in 2012. “There are fewer pairs of Arctic terns breeding in the Gulf of Maine, and those terns that do breed are producing fewer chicks. They’re doing very poorly,” says refuge biologist Linda Welch.
Similar declines reported by the Netherlands and Iceland suggest that more than a local factor is to blame. Some researchers suspect climate change is disrupting the food chain in the birds’ wintering grounds. “So it might be the birds can’t find enough food to rebuild their body stores and regain the energy they need to fly from Antarctica all the way back to the coast of Maine in good enough shape to start breeding again,” says Welch.
Or take the Great Shearwaters that spend summer in the Gulf of Maine. Satellite tags show the large birds forage across the entire gulf – not just near the coast, says Welch. She hopes developers will consider that in deciding where to place proposed offshore wind farms. “Other research projects have shown that most of the seabirds along the Mid-Atlantic funnel close to the shoreline. In some cases, they say that once you go beyond five miles, there are no birds out there. In Maine, that’s definitely not the case.” Because ocean topography varies, she says, a study done in one region may not apply to another.
Bird-tracking devices may also help researchers unravel a mystery: why some Maine seabirds can’t find enough fish to feed their chicks. Arctic terns forage for herring and other small fish at the water surface; unlike puffins and razorbills, they can’t dive for fish. Machias Seal Island once hosted the largest tern colony in the Gulf of Maine. But in 2007, a fish shortage led 3,500 tern pairs to abandon their nests. “They haven’t raised any chicks since,” says Welch.
Other Maine colonies are also having trouble finding food to feed their chicks. “The adult are desperate,” says Welch. “They try to bring in other kinds of fish or invertebrates for the chicks to eat. Sometimes the fish are too big for the chicks to swallow whole. So the chicks starve to death with all those fish carcasses lying around them. It’s really sad.”
While the problem appears worst for Arctic and roseate terns, puffins and razorbills are also affected. At most colonies, puffins are generally able to still produce chicks, but often those chicks are smaller and weigh less, says Welch. “So we don’t know: Are those birds going to survive once they leave the colony? Will they be able to return when they are five to six years old and breed?”
Marine productivity levels, water currents and water temperature all influence the distribution of fish. Increased Arctic ice melt could also affect water chemistry and the location of fish. “It’s not an easy problem,” says Welch.
New tracking technology is making some seabird research easier. For example, nanotags that send data to automated receiving stations let researchers collect data on bird movement without having to retrieve the tagged birds – as is required with geolocators.
But interpretation of bird movement patterns, population changes and productivity rates all rely heavily on visual data painstakingly collected over the past 30 years. It’s not glamorous work. Each summer, seasonal technicians live on the seabird colonies and monitor the seabirds. Peering through binoculars, they document how many pairs return to the colony, how many eggs are laid, how many of those eggs hatch, how often chicks are fed, and which species of fish are brought to the chicks. Researchers compare notes with conservation partners in the United States and Canada who are also monitoring seabird colonies throughout the Gulf of Maine.
“Having a long-term monitoring effort has been critical to our understanding of changes in productivity and seabird diet,” says Welch. “For example, with the Arctic terns, we had 25 years of population growth. Now we have five years of population decline. Our management actions haven’t changed. Our predator control actions haven’t’ changed. So we know something else has changed. This large collaborative data collection effort gives us a much better understanding of the system.”
For its seabird research, the Maine Coastal Islands National Wildlife Refuge received a Rachel Carson Award for Scientific Excellence from the U.S. Fish and Wildlife Service for 2012.
The National Wildlife Refuge System protects wildlife and wildlife habitat on more than
150 million acres of land and water from the Caribbean to the Pacific, Maine to Alaska.
Refuges also improve human health, provide outdoor recreation and support local economies. Visit our home page at www.fws.gov/refuges. Follow us on Facebook and Twitter.
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