Since 1985, U.S. bald eagle rate up 1.7 percent; S.D. down 1.5 percent
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When Chuck Eilts and his wife, Brenda, lived outside of Mitchell, it wasn’t unusual for them to spot a bald eagle on their property along the James River.
After relocating into town, Eilts says he still visits that land from time to time. He’s seen a few eagles this winter, and he said it never ceases to make an impression.
“You still kind of do a double take,” he said. “It’s something interesting you don’t see every day.”
The national symbol, bald eagles prompt fascination by nearly everyone. For some, the search is an active and aggressive pursuit.
Each January, hundreds of state and federal employees and a team of volunteers count the number of bald eagles spotted along specific routes, which vary from a single fixed point to 150-mile areas. The information those teams gather is submitted to a state coordinator who, after reviewing the information for inaccuracies, passes the information along to the U.S. Army Corps of Engineers, where it becomes part of the Midwinter Bald Eagle Count. This year’s survey was completed during the first two weeks of January. The results will be part of a count released in 2010.
The count is designed to monitor trends in the activity of bald eagles, a bird that was listed as endangered in 1978 after it was determined the population and its habitat were threatened by poachers and the use of the now-banned chemical DDT, which causes a thinning of the shell of the eagle’s egg.
On June 28, 2007, the bald eagle was removed from the endangered list, lending proof to the once rare bird’s comeback.
Recent results from the Midwinter Bald Eagle Survey show that of the 43 states that participate, 32 are showing an increase in the number of bald eagles spotted by observers.
The survey results are based on an aggregate collection of data collected from 1986 to 2005.
Overall, the results are showing positive trends in bald eagle reproduction and survival rates, with a 1.7 percent increase in the number of bald eagles observed and 63 percent of routes showing a numerical increase.
Wade Eakle, the national survey coordinator and an ecologist for the USACE, said the results are showing a change in the bald eagle’s migratory habits.
Eagles feed mainly on fish, although small mammals can also become part of its diet. It’s a partially migratory bird, meaning it will only move when the body of water it primarily feeds from freezes.
In South Dakota, for instance, bald eagles are especially evident during the winter along open stretches of the Missouri River. Locally, the birds often can be spotted along open segments of the James River, including the stretch of water just east of Mitchell.
Although bald eagles appear to be thriving in many areas, it’s not necessarily so everywhere.
The annual surveys show that the southwestern United States have seen small declines in eagle population, Eakle said, which could be a result of an increasing human population in the area.
From 1986 to 2005, Arizona showed a 1.3 percent reduction. Other decreases over the same time period include Oklahoma with 0.5 percent, Utah with 0.8 percent and Texas with 0.2 percent.
“That’s where people are moving to,” Eakle said. “There could be an increasing loss of suitable habitat for eagles as the human population moves there.”
Another factor affecting eagle population shifts could be climate change, Eakle said. Warmer winters in some states mean the eagle simply doesn’t have as far to travel to escape the frigid temperatures of the north.
“I think that’s why we’re seeing, in the southwest part of the country, declining trends,” he said. “There’s less of a need to come further south.”
It’s an explanation for the increase in eagle numbers in states like Iowa, Indiana, Iowa and Kansas, all of which have shown “significantly increasing trends,” Eakle said.
While the survey results show generally positive results, Eakle said efforts to strengthen the eagle population will continue.
Eakle said the Army Corps of Engineers, which operates hundreds of manmade reservoirs and lakes across the country, sometimes take measures to help the eagle population flourish.
In some cases, government employees will attempt to reintroduce eagles through a process known as “hacking,” where young eagles are released into an area with the hope that the birds will reach maturity and breed.
Seasonal closures of eagle-friendly habitat – such as tree groves along waterways – are also utilized in areas with known eagle populations.
“If there are areas that receive a lot of recreational use, we might have closures to discourage boaters and people from going in and potentially disturbing eagles during their breeding time,” Eakle said.
As for South Dakota, the survey shows that populations have slightly declined since 1986. However, Eakle said the decline of 1.5 percent isn’t anything to be concerned about.
“It’s not a significant difference from just a zero change year after year,” he said.
There are four routes in South Dakota where 71 surveyors gather information about the state’s eagle population. Numbers are monitored at routes along Lake Frances Case, Lake Oahe, Lake Sharpe and the lower Missouri River.
The numbers can vary wildly from year to year. While the survey only shows results up to 2005, numbers provided by the USCGS show that South Dakota had a total of 40 eagles at Lake Frances Case from 2006 until 2008. Between 1994 and 1996, the same area had a total of six.
In 2007, there were 226 bald eagles spotted along all of South Dakota’s routes.
Eakle said that surveyors are strongly encouraged to document sightings as accurately as possible.
“Frankly, it isn’t that tough,” he said. “If it’s a big bird and it’s got a white head and a white tail, you’re pretty confident that it’s an adult bald eagle.”
Problems can occasionally arise when attempting to distinguish between immature bald eagles and their golden counterparts, Eakle said, but surveyors are encouraged to be honest on submission forms.
“We encourage people not to stretch their identification skills,” he said. “If it’s a bird you simply can’t identify to either species, you note that on the form.”
Eakle said he’s encouraged not only by the overall increase in the number of eagles observed nationally, but also in the interest in the survey program itself.
“I think eagles are always going to be popular with the public,” he said. “Because it’s our national symbol, that’s one of the reasons why there’s such a high level of interest from folks still doing this midwinter survey.”