The American Bald Eagle Foundation counted 1,524 bald eagles in its first aerial survey during peak eagle activity in the valley since 2000.
Wednesday’s survey purpose was to find out how many eagles are in the area for the fall congregation, which normally peaks in late November, said Chloe Goodson, the foundation’s education and outreach coordinator.
The U.S. Fish and Wildlife Service conducted ground and aerial surveys annually from 1986 to 2000 until funding was no longer available.
The annual maximum count from the aerial survey in 2000 peaked at 3,444 eagles, the highest recorded, according to federal data. But the 2000 and 2016 numbers cannot be directly compared because of differences in how the aerial surveys were conducted and other natural variables.
There was no data collected from the ground or the air from 2000 to 2008 until Haines resident Pam Randles took over ground counts in 2009. Randles passed all of her data and the federal fish and wildlife information to Goodson when she took over ground surveys last month.
“I want to go back in time and get that data,” Goodson said about the eight-year gap in all eagle data, and the 16-year gap in aerial data. “The data that’s been missed for so long is an important piece to the eagle puzzle that can never be recovered.”
Goodson and pilot Drake Olson with Fly Drake went up in Olson’s Super Cub plane for about two-and-a-half hours to count bald eagles at specific data points from the air.
Goodson spoke with John Hodges, pilot and former U.S. Fish and Wildlife Service biologist, about how to conduct the surveys as they were done in the past and what paths to fly in the valley so data may be comparable to years past.
“What’s going to be as important is the actual parameters of the flight,” Olson said. Olson flew in a grid pattern. Goodson said Olson looped around to make sure eagles were counted in very dense areas.
Although Goodson tried to use the same data points as the surveys that ended 16 years ago, there were slight differences in geology due to landslides and other natural movements.
Fish and Wildlife raptor biologist Steve Lewis was concerned that the foundation may not be able to compare its data to past years’ information because of unknowns about conditions in the two time periods.
“When you fly a survey like this, you really don’t know how many birds you’re seeing,” Lewis said. Lewis said detectability – how many birds are really present compared to the number of visually counted birds – was identified as a major issue in all wildlife data collection in the early 2000s.
One way to avoid that problem would be to repeat an aerial survey two or three times in one day, assuming the percentage of birds the observer misses each time is relatively the same, and then repeat that on different days in the season, Lewis said. But with that method, cost increases significantly.
“It’s kind of a sticky problem,” Lewis said. Two observers counting eagles on either side of a plane could also help decrease the detectability issue. The U.S. Fish and Wildlife Service used two observers in a plane in the late 1980s and 1990s.
The foundation pays $250 an hour for one observer, Goodson, to conduct the count. A second person would cost an additional $200 an hour. Goodson said the foundation is going to seek money through fundraising or grants to keep these aerial surveys going.
During the count, Goodson said she was equipped with two clicker counters, one for single eagle counts and one to record every 10 eagles. She intends to repeat the survey at least one more time this season.
Other variations in data from year to year could result from differences in the time of day, weather, food availability and more. Goodson wants to look over salmon data and weather data to compare it with bald eagle data to get a better idea of how those relate.
“There’s a lot more in-depth eagle research in the valley that could be done that’s not being done currently,” Goodson said. Some of that research includes tracking eagles with radio tags – solar-powered tracking devices similar to GPS equipment – which was last done in 2014 in Haines by researcher Rachel Wheat.
Lewis took part in aerial nest surveys in the last several years related to future Haines Highway construction plans. The surveys documented nests to find which ones were occupied and later contained young.
Lewis said the foundation should be able to get an index of the eagles in the valley with these aerial surveys. All things being equal, Goodson should be able to identify a relative change over the season, he said. But keeping consistency across time is difficult.
Lewis noted the community wants a “yes” or “no” answer on if the valley’s eagle population is shrinking. A bigger investment in aerial surveys is needed for that, and the ground survey data would need to remain consistent, he said.
Haines’ tourism industry uses the bald eagle numbers to attract visitors, especially during the American Bald Eagle Festival in November.
“We’ll be able to have cold, hard facts instead of educated guesses and abstract thoughts on eagle populations near Haines. These counts help to provide accurate trends in bird abundance during the year,” Goodson said. “And as a member of the (foundation), I am dedicated to research of our national symbol.”