Two years ago when Allison Byrd came to the University of Maine to begin her graduate research on loons, she didn’t know much about the large birds.

She quickly found out that’s not true for Mainers.

“Everybody in Maine has a loon story or has seen them,” Byrd says. “(Loons) are so iconic and well-loved. Even when I first came to Maine and stopped at a rest stop, there was a big picture of a loon.

“To be honest, I was a little intimidated at first. (Then) I realized, OK, I’m really going to have to know my stuff.”

Two years later, Byrd has gotten closer to more loons in Maine and around the country than most people ever will. Working under UMaine assistant professor Brian Olsen, Byrd is studying the potential effects of climate change on the loon population in Maine and the nation.

Loons — in Maine the species is the New England common loon (Gavia immer) — are not endangered, but there is much value in data about them. A loon can live more than 30 years, which is relatively long for a wild bird.

“It’s important to understand population dynamics as the long life span of a loon makes it harder to detect declines in abundance,” says Byrd, who graduated from the University of Rhode Island with a degree in wildlife biology. She went on to do fieldwork on black bears and had a job in a fish hatchery in her native New Jersey, worked as a zookeeper in Boston, and did fieldwork with birds in Australia, Mexico, Panama and the U.S. before coming to UMaine to work on her master’s in ecology and environmental science.

Initially, Byrd was interested in loons because of their unusually aggressive behavior. Loons will kill each other in fierce territorial clashes, which brings up a key question: Why defend one’s territory to the death when moving to another lake would seem simpler? That leads into Byrd’s research on why loons settle where they do, and how vulnerable the birds are to changes in their habitats and the climate.

“In Connecticut, for example, there are suitable lakes and habitat, but there are no loons,” she says. “There is something that’s limiting the edge of their range, whether it’s water clarity, lake surface temperatures, fish assemblages or dissolved oxygen levels. The question is: Are those the same things that are predicted to be affected by climate change?”

The research combines demographic analysis, physiological measures and behavioral observations of loons across a range of climatic conditions to predict how changes to lake characteristics could impact loon distributions.

To that end, Byrd spent the past two summers banding loons on lakes in the areas of Rangeley and Greenville in western Maine. She also traveled to Montana and Washington state, and recruited biologists in other regions with loon populations to gather behavioral observations of territorial loons.

Byrd will combine her more than 2,000 recorded observations with analyses of lakes — both with and without loons — to build a model that shows why loons locate where they do. That model will indicate what will happen to loons if there are climate change-related shifts to lake characteristics.

The process of loon banding presents a challenge even before a loon is ready for a band on its leg. If threatened by something such as an approaching boat, a loon will dive underwater, making it impossible for researchers to grab the bird. However, if a loon has chicks that are too young to dive, the adult is more likely to stay on the lake surface. Banders work at night, approaching quietly in the darkness, before turning on a spotlight when they close in on the loon. The light is so bright that the loon cannot see the boat, and the loon is scooped up with a net.

If a loon looks as if it might dive despite the light, banders imitate or play sounds of chicks in distress. The sounds momentarily confuse the loon, which will likely stay on the lake surface rather than abandon its chicks.

“Everything is very quiet and calm to that point, but things get a little more hectic when you scoop it up because the loon is huge and strong and fighting,” she says. “Then you get it into a position where it can’t hurt itself, hold it, take blood samples. If it’s not (already) banded, you put bands on it, and take bill measurements and other measurements for body size. You release the adult and chick together.”

Banding and behavioral observations gave Byrd two key statistics. First, she was looking at questions of presence/absence — where loons are living and successfully having chicks, and where they are living but not pulling off young. Second, she considered site fidelity — how likely loons are to return to the same lake year after year.

“Thanks to banding, I can look at how often birds come back to a territory, which is going to help understand if that’s a preferred habitat,” Byrd says. “If there’s one lake with a different bird every year, we can start to guess that that’s not a good territory or conversely, it’s a great territory and they’re fighting hard every year and every year someone is getting kicked out. But that’s a little less likely because loons are good at maintaining their territory.”

Byrd took blood samples from loons in Maine, New Hampshire, Montana and Washington state. Part of Byrd’s funding and her long-term dataset, which contains historical banding records and site fidelity information, comes from the Biodiversity Research Institute (BRI), a Gorham, Maine-based nonprofit whose mission is to assess emerging threats to wildlife and ecosystems through collaborative research. Byrd uses the blood samples to look at metabolite measures that indicate how well an individual loon is preparing for its winter migration. BRI is also interested in assessing the effects of mercury on ecosystems.

Because loons are usually near the top of the food chain in their environment, they are a good bioindicator of the accumulation of mercury in a system.

Spending so much time around loons, Byrd has learned something else about the species. Those loon calls we associate with the tranquility of summer on a Maine lake are actually, for the loon, an indication of something a lot less tranquil.

“When they call out in the middle of the night, it’s thought that they’re doing that because it’s quieter or the sound will travel farther, saying, ‘Here’s where I am, this is my territory,’” Byrd says. “If you hear the yodel, that beautiful sound that is so iconic, and if you look around, there might be another loon or an eagle flying overhead. They even respond sometimes to low-flying airplanes. What they’re saying is, ‘I’m ready to take you on if I need to.’”