Bald eagles, as I’m sure you know, are making quite the comeback in New Hampshire (along with much of North America). New Hampshire Audubon and the Loon Preservation Committee wondered what effect this large fish-eating predator was having on another iconic fish-eating bird, the loon.
The answer, they say, is “not much”.
The team looked for evidence of predation attempts by an increasing eagle population, and whether this was limiting how successful loons are at raising young or if eagles provoked changes in where loons nest. The scientists found that eagle nest proximity may be contributing to about 3% of observed loon nest failures, but that this pressure does not account for local declines in loon abundance. Loons face a wide range of other simultaneous threats, including mortality from lead tackle poisoning, avian malaria, and entanglement in monofilament fishing line.
“We confirmed that eagles have joined a wide range of stressors currently impacting loons in New Hampshire,” said Loon Preservation Committee Senior Biologist John Cooley. “This result is great motivation to keep reducing the impacts caused by humans, like lead tackle poisoning, so that eventually the primary challenge for nesting loons can once again be natural predators like eagles.”
Here’s the rest of the press release:
A partnership between NH Audubon and the Loon Preservation Committee tells us more about the interactions between two of New Hampshire’s most iconic birds sharing the state’s lakes and rivers. The two wildlife conservation groups collaborated on an innovative study examining 16 years of breeding data for both Bald Eagles and Common Loons to evaluate what influence nesting eagles had on loon territory occupancy and productivity. A major article describing their findings appeared recently in the Wilson Journal of Ornithology.
For nearly 40 years, NH Audubon has partnered with NH Fish and Game to monitor and manage Bald Eagle population recovery. The Loon Preservation Committee has a 45-year history of fostering Common Loon population recovery in the state. Loons remain on New Hampshire’s threatened list, while eagles were taken off the state’s threatened list in Spring 2017 because of significant progress toward full recovery.
NH Audubon President Doug Bechtel noted, “It’s interesting how loon and eagle populations have recovered to the point where we’re seeing more interactions between these two highly visible fish-eating species, something that probably used to happen regularly before they declined.”
Bald Eagles are known to steal fish from loons, sometimes harass incubating adult loons, and occasionally prey on loon eggs or chicks. Managing interactions between these species of conservation concern is challenging, particularly since so much evidence is anecdotal.
When data collection for this study concluded in 2013, there were 284 territorial pairs of Common Loons (pairs that defend a breeding territory for a minimum of 4 weeks and have the potential to produce offspring) and 40 territorial pairs of Bald Eagles. Biologists now estimate that there are some 313 territorial pairs of loons and 72 territorial pairs of eagles in the state. In other words, in the last six years the state’s loon population has risen by 10% but the state’s eagle population is up 80%.
Collaborating on the study were Loon Preservation Committee Senior Biologist John Cooley, NH Audubon Conservation Biologists Chris Martin and Vanessa Johnson, as well as volunteer statistician David Harris.
“For me, the single biggest take-home point is the incredible value of these long-term data sets,” said Martin. “Both LPC and Audubon gathered data on our respective species of concern for years. Then we realized that combining our data allowed us to ask and answer new and important research questions.”
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I live in Thomas Pond in Casco, Maine. My past time now (stay at home order) is to observe what’s happening on the lake. New to area, new to understanding birds but I just held my breath as I saw an eagle circle then dive bomb 2 loons. Nothing happened but so afraid eagles will run off/kill the loons. Any info you can refer me to about eagles and loons? Thanks so much.
There are too many eagles and they are devastating loon chick populations. With two consecutive years of decline in loon chicks and eagle predation sited as one cause by Maine Audubon, we have a big problem. I have watched them double up on the loons until they cannot protect the baby and they take them. Thus is no different than reintroducing wolves.
Saw a bald eagle attack a mama loon and her baby the other day on Branch Pond. Mama was very brave and the baby survived but the eagle is still circling around.
On Crooked Lake in Petoskey Michigan, we have had a successful loon platform for several years. The loons are back again this year. For a week they have been visiting the platform on a daily basis but have not been seen on the platform. Today an American Bald Eagle harassed them for 30 minutes until they left the mile-long protected bay where the platform is located. In past years eagles have been present occasionally but have not been a problem for the loons. I do not know where the eagle nest is but it is likely within a half-mile of the platform. Is our best course of action”Let Nature take its course”? Or, are there suggestions to help the loons?
I doubt if there’s anything you can do, short of killing the eagles, which isn’t a desirable (or legal) remedy. Nature red in tooth and claw, etc.
David, Thank you for the confirmation. “It is tough out there” in the real world.
Follow-up comment – see prior posts: About two weeks ago I posted that an eagle was harassing the two loons that were in the process of claiming this quiet bay and a well-placed loon platform (probably the same loons that have had successful chick hatches here for the past 5 years). I was worried that the eagle would run them off this year. GOOD NEWS FOR THE LOONS: The eagle only bothered the loons for two days. I have not seen the eagle for at least ten days. The loons have successfully nested on the platform and laid their first egg on May 7. We hope for two chicks on or about June 5. The eagle may have found other hunting grounds for now but when the chicks hatch we may need to worry about the eagle going after the chicks.
Watched a bald eagle divebombing a loon pair in open water. Repeatedly. I think it got at least one chick earlier by the loons calls. Then they switched to the “intruder call” of the male just before we walked to the cove and witnessed the attacks. Felt pretty sorry for the loons.
Predation by the growing bald eagle population is one of the risks that the Loon Conservation Assoc. lists on their website.
Nothing is straightforward in Nature: “Eagles are back – hooray! Loons are threatened as a result – boo!”