Science

Watch: Female Hog Island Osprey Defends Remaining Chick From Great Horned Owl

Having already lost two chicks to the raptor, Rachel has been remaining close to the nest and on high alert in a fascinating display of adaptation.

By Andrew Del-Colle

Digital Editorial Director, Audubon Magazine

Published July 21, 2017

It's been a dramatic two weeks for Rachel and Steve's family. Early last week a Great Horned Owl attacked in the middle of the night and took a chick from the Osprey couple's nest at Audubon's Hog Island in Maine. Then, a few nights later, it returned for seconds. Even for a nest cam that has captured its share of nest attacks and historic moments, this has been an especially eventful 12 days.

Since the attacks, viewers of the cam, which is hosted by explore.org, have been anxiously watching to see if the owl would strike again and Rachel would be able to protect the lone remaining chick (as noted in our story about the first attack, male Ospreys don't usually defend their nests at night). In response to the attacks, Rachel has stuck closer to the nest, and that paid off last night when presumably the same Great Horned Owl returned for round three. This time, though, Rachel was ready.

As can be seen in the video above, the clip opens up almost right away with an attempted attack that Rachel manages to thwart. Then, at the 2:57 mark, the Great Horned Owl appears in the background, landing in the bough of an evergreen to survey the situation. After a full minute, it takes wing again, disappearing from view. Rachel, who is sitting on the edge of the nest, clearly spots the bird, though, as she begins loudly emitting her warning calls. The owl swoops in anyway and attempts to land on a large limb sticking out from the nest, only to be chased away. Undeterred, the owl returns again at 5:45 for one more attempt. But Rachel digs her talons into its back and once again defends the nest. It's not clear if the chick was harmed during the attacks, but it at least got to survive to see another Hog Island sunrise.

While it's been captivating to watch this saga play out, Rachel's adaptations to the attacks are illuminating in an evolutionary and biological sense. We once again asked Steve Kress, who works on Hog Island and is Audubon's vice president of conservation and director of seabird restoration program, for his thoughts on this latest news. Here's what he wrote back in an email:

"There is a lot of insight about how individual predators learn new and ingenious ways to capture prey. What is surprising here is that Rachel seems to be learning new ways to defend her remaining chick. Predator-prey interfaces are often thought to be driven by selection favoring specific behaviors that then become genetically hard-wired, but if Rachel is changing her behavior by perching lower and closer to her chick, it appears she is learning from her experience and adapting her behavior to be a more successful parent. The camera is once again showing new and very exciting insight to bird behavior."

Considering the owl clearly realizes that there's one remaining meal in this nest, there's a good chance that this isn't the last time Rachel will have to fight it off. However, she might not have to keep up the defense for too much longer. Last year's brood fledged in early August, and this chick is getting very close. If Rachel can keep the owl at bay, the chick might just be able to leave this nest—and all its drama—far behind.

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