Lake Sonoma joins nationwide midwinter bald eagle survey
Story and photo by Brandon Beach
District Public Affairs Office
U.S. Army Corps of Engineers officials conducted their annual midwinter bald eagle survey at Lake Sonoma, Calif., earlier this year. Typically, up to as many as five eagles are counted at the lake per year.
Data from the survey is collected during a two-week window in January and forwarded to the U.S. Geological Survey for inclusion in a national database set up to monitor eagle populations in the lower 48 states. Various wildlife agencies and other private volunteer observers also participate in the midwinter count.
The survey was first held in 1979 by the National Wildlife Federation. Back then, bald eagles were in a fight to stay alive.
“At that time, we had just a few 100 bald eagles nesting in the lower 48 states,” said Wade Eakle, an ecologist with the USACE South Pacific Division, who worked with Joe Lishka, a USACE San Francisco District park ranger, and Dr. Monte Kiven, a nationally-recognized expert on raptor management, in completing the bald eagle count at Lake Sonoma.
Widespread use of DDT and other pesticides in the 1950s and 60s led to infertility in eagles. The effects of such chemicals were eventually discovered, and a ban was placed on their use in 1972.
“Eagles today are no longer laying thin-shelled eggs,” said Kiven, a biology professor at Santa Rosa Junior College. “That has a lot to do with their reproductive success.”
Wildlife experts estimate that up to 6,000 nesting pairs of bald eagles live in the continental U.S. today.
At Lake Sonoma, park rangers are aware of one nesting pair of adult eagles that have been residents of the 2,700-acre lake since at least 2001, the year they were first discovered.
“They are here year-round,” said Lishka. “They alternate between two nesting sites. It’s typical for eagles to have more than one nest. ”
Other bald eagles migrate seasonally to Lake Sonoma, some traveling as far as the northwesternmost province of Canada.
“We know this because [U.S.] Fish & Wildlife Service has branded some of these eagles, and they return year after year,” said Kiven.
With plentiful food options like fish and small mammals, Lake Sonoma and its surrounding forest areas provide “critical habitat for eagles,” said Eakle. “With its lakes and parks, [USACE] has always played a key role in the recovery and conservation of bald eagles across the U.S.”
Data collected from this year’s survey will be used to conduct a 25-year trend analysis of wintering bald eagle populations in the continental U.S.
The eagle was declared an endangered species in 1967. In 1995, it was reclassified to the less-severe “threatened” list as its numbers began to rebound, and, in 2007, it was completely delisted.
“Eagles have recovered,” said Eakle. “It’s important now to monitor their population post de-listing to make sure they don’t start declining back towards extinction like it did 40 years ago.”
For more on the history of the bald eagle, visit www.baldeagleinfo.com.
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A bald eagle is spotted near the park entrance at Lake Sonoma. |