JACKSON, Wyo. — Jackson Hole’s ospreys migrate back to their summer range every spring in an effort to claim their nests along the Snake River.
Teton Raptor Center Conservation Director Bryan Bedrosian spoke to Buckrail about the valley’s osprey populations. After being impacted by DDT — a pesticide used to control insects in the ’70s and ’80s — Wyoming’s osprey populations are now doing well, Bedrosian noted. He said that returning ospreys will migrate back to the valley from faraway winter ranges.
“We tracked a number of ospreys with transmitters over the years,” Bedrosian said. “Almost all of them from the Jackson Hole area are going somewhere along the Gulf Coast. We have a number that go to the Yucatán Peninsula in Mexico, Louisiana and Texas. We had one crazy dude that went down through Florida and into Cuba.”
Bedrosian said that the solar-powered transmitters, in best-case scenarios, can last up to nine or 10 years, if they don’t fall off or fail.
“I personally like to do a method where the transmitter falls off,” Bedrosian said. “If you have an eagle or an osprey that lives 10 years, and a transmitter that might only be good for three to four years, ethically, I’m not super keen on having a non-functional transmitter on an animal. I put a little break-away on there, so it will usually fall off after two to three years.”
Bedrosian said that ospreys will migrate independently, returning to the same spring and summer territory every year solo. If an osprey’s mate from the previous year shows up, then they will mate again, but will pick up a new mate if needed. The bird’s nests are almost always near rivers, including the Snake River, Gros Ventre River and a few along the Hoback River, with the largest number of ospreys residing along the Snake River corridor.
Bedrosian estimates that Jackson Hole has approximately 40 osprey nests, with the raptors typically returning to their same nest year after year.
“Osprey nests are like homes in Jackson — they are hard to come by,” Bedrosian said. “If you find a nice affordable, you stick to it. So, there isn’t much movement in between because there are a limited number of nest sites that the birds can climb onto.”
While the birds are capable of building a nest from scratch, they often take advantage of the built platforms that can be seen throughout the Snake River valley.
“The reason why we have so many platforms is because an osprey’s wings are super wide, and they are super clumsy when it comes to perching,” Bedrosian said. “They have to have a perch and a nest that doesn’t have branches above it.”
Bedrosian explained that the birds have adapted to building nests on power line structures, often situated at the ideal height for their nesting habitat. Since it’s “not good for the power lines or the birds,” Lower Valley Energy (LVE) has constructed platforms to accommodate osprey populations. He added that over the years, osprey have been “artificially moved” toward selecting the man-made structures.
Bedrosian told Buckrail that an ongoing issue has been Canada geese taking over the platforms, since geese nest earlier in the season.
“The Canada geese will come in and take over a nest and then the osprey will try to build another nest on the power lines,” Bedrosian said. “LVE will come in and build another platform. So, there are areas where you’ve got multi-platforms within a given territory.”
To keep the geese away, Bedrosian started building tilting platforms that can be raised and lowered at a 45 degree angle. The platforms can be lowered into the flat position when the osprey return to the area.
Bedrosian commented on why the birds have such a widespread appeal.
“They are recognizable, they’re big and they’re in areas where we see them,” Bedrosian said. “I like to think that most people love raptors, especially one that is catching a fish. If you see one catching a fish, it’s super cool, especially because it’s interacting with nature in a way that is accessible.”
Ospreys primarily consume fish, and Bedrosian guesses that an osprey “hopes to catch one fish per day” in order to stay healthy. Ospreys have an internal polarization of the eye, as well as an adaption to turn a toe backwards to more easily catch fish. He explained their unique hunting abilities.
“They hover and dive down into the water,” Bedrosian said. “They can go upwards of 4 to 5 feet under the water to catch a fish, as opposed to an eagle that’s just going to skim the surface, and grab something that’s just on the surface.”
Chicks will typically fledge in late July, often returning after departing the nest, opting to stay at the nest longer than most other birds.
“What we’ve seen from tracking family groups, is that once the chicks are old enough to fly, the mom will leave,” Bedrosian said. “She’s like, ‘I’m done,’ and she takes off. She leaves the chicks to dad. Dad will stick around to take care of them. One by one, the chicks will leave for migration in the fall. After the last one leaves, then dad will migrate.”
In their first year of life, ospreys will spend a year and a half along the Gulf Coast before migrating back to the valley at the age of two.
“Every other bird, when they migrate in the fall, will come back that next spring,” Bedrosian said. “Young ospreys skip the first migration, and over-winter in the Caribbean, which sounds good to me.”
