In August 2009, an Atlantic puffin left Seal Island National Wildlife Refugeand flew northeast, through the outer Gulf of Maine and along the continental shelf of Nova Scotia, eventually reaching the Labrador Sea. Then, at the end of January, the puffin flew south, almost as far Bermuda. In May, he returned to Seal Island for the summer before repeating his Atlantic journey the following winter.

Until this puffin was captured at Seal Island in the summer of 2011, and the details of his journey retrieved from the GPS device that had been secured around his leg by the National Audubon Society, no one knew where puffins went in winter. Another puffin that was tracked flew a similar route, but did not travel quite as far.

The extensive travels even surprised Dr. Stephen Kress, the man largely responsible for re-establishing puffins in Maine when he moved chicks from Newfoundland to Eastern Egg Rock in the 1970s. Today, the Atlantic puffin is a “life list” species for avid birders, and puffins have become symbolic of the Maine coast, where their population has rebounded to 1,000 pairs nesting on offshore islands.

“I did not expect them to travel as far as they did,” said Kress, who directs Audubon’s Seabird Restoration Program. “They’re short-winged little birds—their wings beat 400 times per minute—why would they travel any farther than they had to? We can only begin to guess why they do this. The fact that they are moving so much suggests that puffins have different needs throughout the winter. We also don’t know if these two birds are typical. It’s really just the beginning of the story.”

Knowing where puffins go during the eight months of the year when they are not in Maine will help Kress and other wildlife biologists identify important marine bird areas at sea and focus conservation efforts. “We don’t just manage wildlife in one place, but over its entire habitat,” said Kress.

Puffins and other seabirds can tell us not only where they go, but also reveal the changes affecting their nesting habitat and migration routes. Birds migrate—and stay put—for multiple reasons. Birds need clean water, clean air and clean food—lots of food.

It takes food to raise a seabird chick, and most of that food is fish. Without enough of the right size and type of fish available in surrounding waters, seabird nesting colonies do not fare well. This is one reason that seabird nesting colonies have variable success rates year to year; seabird nesting success indicates the health of the immediate environment surrounding the colony.

Puffins are alcids, a family of birds that includes murres, guillemots, razorbills and the extinct great auk. Alcids dive for fish hundreds of feet down in the water column—the same fish that are eaten by larger fish and marine mammals. But unlike large fish, seabirds eventually come ashore, where humans can intercept them. Concentrated in their colonial hubs, seabirds can be sampled and monitored.

The health of migratory birds when they are here in Maine reveals something about life in the other places they visit. It’s hard to know what goes on beneath the vast surface of the Gulf of Maine. The perpetual disagreement about the health of fish populations among fishermen, scientists and regulators is testament to this great unknown. Scientists can look at seabird health and diets as a proxy for trends in fish populations, and the broader ocean ecosystem.

In addition to being perpetually hungry, birds are also fairly predictable. Take the puffin’s cousin, the common murre. Murres feed almost exclusively on capelin, a small schooling fish that is also a primary prey item for cod. But the capelin in murre stomachs have gotten smaller and less nutritious in recent years, affecting the health of murres and probably cod, too. By studying the murres, researchers Gail Devoren of University of Manitoba and Bill Montevecchi of Memorial University have gained a glimpse into the complex and mostly hidden submarine food web.

Seabirds can also signal larger shifts.

When Montevecchi began studying gannets on Funk Island near Newfoundland, Canada in the 1970s, the large, skydiving seabirds were eating mackerel, saury and squid. Then, in the early 1990s, their stomachs became full of capelin, herring, juvenile cod and sand lance, species typical of colder water. The seabird diet shift revealed a biological regime shift at the same time that oceanographers and climate scientists had documented a physical oceanographic shift, due to an influx of cold, fresh Arctic water into the North Atlantic. According to Montevecchi, from 2005 onward, warm water has allowed the return of migratory warm-water pelagic species, including Atlantic mackerel, Atlantic saury and short-finned squid, into the gannet diets.

Stephen Kress has seen a similar phenomenon in puffins. Atlantic herring are the traditional diet of the puffin, but herring are becoming less important as puffins feed more on warm-water species like saury. Research by Maine Coastal Islands National Wildlife Refuge staff during summer 2010 and 2011 documented a similar shift in the diet of terns as well, which now bring butterfish, rather than herring, back to chicks in the nest. Butterfish, a warmer water fish, is rounder in shape and harder for chicks to eat, a fact which Refuge biologists think has contributed to lower survival rates at tern nesting colonies in recent years.

Birds are sentinels for the health of the broader ecosystem. There’s a reason it’s a “canary” in the coal mine and not some other animal. As effective ecosystem samplers, birds are not only emblematic animals that people travel to world to see, but also provide subtle clues to how our ocean environment changes in time.

This article is made possible by funds from Maine Sea Grant.

Heather Deese holds a doctorate in oceanography and is the Island Institute’s vice-president of programs. Catherine Schmitt is communications coordinator for Maine Sea Grant.

The National Audubon’s research was funded in part by Sea Grant.