Danger In the Nest: Osprey and Baling Twine

For the last six years, an adult Osprey pair – “Charlotte” and “Charlie” - have delighted viewers around the world as they build a nest and attempt to raise a family each year on the nesting platform in Charlo, MT. Charlotte and Charlie have successfully raised 11 chicks since 2016.


This year, Charlotte and Charlie first appeared in mid-April, when they migrated thousands of miles back to Montana from Central or South America where they spend the winter. After spending some time bonding and getting their nest into tip-top condition, Charlotte laid two eggs. They kept the eggs warm by incubating them for over 5 weeks. Those eggs hatched around June 13 and 16. Right around the same time, Charlie brought baling twine into the nest.


Two osprey chicks in a nest. One is badly tangled in baling twine.
A picture of the two osprey chicks in the nest, before the twine was removed the first time. The younger, smaller chick is at the edge of the nest near the top of the image. The older, larger chick is in the center of the image entangled in orange baling twine. They are less than two weeks old and still completely reliant on their parents for survival.


What is baling twine? How do Osprey get it?

Baling twine is a strong, thin rope that is used to hold together bales of hay. Today, it is most commonly made of many fine strands of polypropylene, a plastic polymer. Polypropylene baling twine can take half a century (or longer) to break down- much longer than the natural lifespan of an Osprey. When discarded baling twine is left in a field or pasture, Osprey will pick it up to use as nesting material, lining the nest and building it up. This can have devastating consequences for the birds.


Why is baling twine dangerous for Osprey?

Osprey sometimes use bits of human refuse as nesting material: bathing suits, flip-flops, fishing line and plastic balloon ribbons, rubber gloves, a copy of the local newspaper still in its plastic bag—and their favorite here in the West: baling twine. It is thought that Osprey consider these to be similar enough to their natural nesting materials that they pick them up and bring them home. Baling twine is abundant in many Osprey nests on artificial platforms near agricultural areas where it is commonly used, as Osprey pick up nesting material from within about half a mile of their nest.

Since baling twine is plastic, it is extremely difficult to snap or break, and it doesn’t break down quickly in inclement weather—qualities that make it ideal for holding together hay bales, but can be deadly for Osprey if they get tangled in it. Though Osprey have sharp talons and beaks, they’re not sharp enough to cut through the twine—Osprey talons meant for puncturing and ripping apart fish, not cutting through rope (think ice picks, not box cutters).


Adult Osprey tangled in baling twine can become unable to fly and trapped in their nest (or stuck dangling from the nest) or can slowly lose toes—or a leg—due to cut-off circulation. When the chicks are tangled, they are less able to move around in the nest, which means they are less able to get to food their parents bring back, and they can slowly be outcompeted by their larger siblings and starve. If the baling twine is wrapped tight around a leg or wing, the chicks can lose limbs or toes, which means they won’t be able to hunt and will slowly starve if they make it to adulthood. It’s estimated that up to 10% of osprey chicks in the West will die from baling twine in the nest.


See Montana Osprey Project FAQ, Baling Twine and Raptor View Research Institute: Baling Twine Project for more information on why baling twine is dangerous for osprey nests in Montana.

Baling twine in the Charlo Osprey nest

We had been monitoring the baling twine Charlie brought to the nest, and quickly sought advice from local Osprey and raptor expert Rob Domenech, the executive director of Raptor View Research Institute (RVRI), who explained that disturbing the nest with such young chicks could be detrimental and is generally not advised. Typically the chicks don’t get tangled until they are a bit older and, moving around the nest. RVRI planned to make the trip to Charlo the next week with a bucket truck to access and clean the nest. However, when one of the chicks was tangled in the twine, we had to act quickly to find a local truck operator who could help us access the 35 foot high nest and remove the twine from the bird.


ORI’s non-intervention policy

Overall, ORI has a non-intervention policy in regard to our research and nest cams. The only exception to this is when a situation is caused by humans—such as if a bird is tangled in baling twine, as it was in this instance. As researchers and cam watchers our role is not to influence the natural interactions between species and their environments: our role is to learn, enjoy, document, and promote the conservation of these animals and their ecosystems.


The first rescue mission

The first rescue mission to remove baling twine was on June 28. The most critical issue was gaining access to the nest itself. The nesting platform is 35 feet off the ground, which means that special equipment was needed to reach the nest.


Two people with a bucket truck below the osprey nesting platform.
Chad and Sarah of Chadz Wraps and Signs ready their bucket truck to access the osprey nest, visible on the tall platform behind and to the right of the truck. Chad stands on the back of the truck, and Sarah stands on the ground to the left of the truck, gazing up at the osprey nesting platform.

Beth quickly began calling local businesses with bucket trucks to see who was available to come help. Eventually, she reached Chad Killorn of Chadz Wraps and Signs, who agreed to help, though he was out of town on a job and wouldn’t be back until later that evening. Then, on the way back, his main truck broke down. Despite this, he agreed to try to bring his second, older truck out, though he wasn’t sure it would work. He and Sarah graciously gave up their evening and family dinner time to meet Beth and Chloe Hernandez, ORI’s intern, at the nest.


Beth conferred with local raptor experts Rob Domenech (RVRI) and Brooke Tanner of Wild Skies Raptor Center (a rehabilitation facility) while she was at the nest.


At the nest, Beth cut away the baling twine that was tightly wrapped around the chick’s leg, carefully cutting it away strand by strand from the chick’s swollen leg and foot. She also removed all the other baling twine from the nest. She identified this chick as the oldest of the two, based on the development of tail feathers (the other chick hadn’t started to grow any in yet, while this one had tiny feathers just starting to grow in).


Based on recommendations from Brooke and Rob, she left the chick in the nest to hopefully recover. It is generally not considered best practice to remove a young nestling from the care of its parents. At this young age, Osprey have a good chance to regenerate, recover, and develop normally from injuries. It was estimated any injuries could take about 2 weeks to heal. Before the rescue crew left the area, they observed both parents back on the nest with a fish, feeding and shading the chicks from the hot sun.


Second rescue mission

Then, a few days later on July 5, Charlie brought more baling twine to the nest. The chick again got tangled, and another rescue mission was organized. It was also observed by the camera operators that the injured chick was not very mobile around the nest. Chad was out of town, so Beth again called around and found a tree service company that was willing to help: Rick Jennison, of Rick Jennison Tree Service in Ronan, Montana. Once he was available (not until 10 p.m. that night), he arrived with his bucket truck and went up to the nest, where he was able to untangle the chick and bring it down to Beth to examine. The injured leg did not seem to be healing, so the chick was taken to Wild Skies Raptor Center for medical attention.


A woman in a bucket truck at the osprey nest untangling baling twine.
ORI Biologist Beth Mendelsohn stands in a raised bucket truck at the osprey platform. She is reaching into the nest to cut baling twine from around the tangled osprey chick. An adult osprey is flying overhead.


Learning the extent of the injuries

At the rehabilitation center, the chick was fed and examined. An X-ray of the leg revealed multiple serious breaks and other injuries. Unfortunately, the injuries were too severe to be a candidate for any kind of medical intervention or surgery, and the chick was humanely euthanized. It was a very difficult and painful decision for the rehabilitation staff. They often see the worst of the worst, doing their best to care for wildlife that have been injured by human activities. This is never a decision wildlife rehabilitators centers take lightly, but in this instance it was the only humane option. Osprey with one leg would not be able to survive in the wild, and also legally cannot be kept in captivity.


Where these injuries caused by baling twine?

Though the chick was initially injured by being tangled in the baling twine, the extend of these injuries suggest something else happened as well. We think that the severity of the injuries revealed by the x-ray suggest an attack by a predator while the chick was tangled in the twine. such a young chick would not be strong enough cause the broken bones that occurred to itself. This seems a likely scenario, as Great Horned Owls are in the area—they nested nearby (in fact, the Great Horned Owls at the Roger’s Place cam, which earlier in the season was pointed on a Great Horned Owl nest, now provides the best view of the osprey nest. The Great Horned Owl chicks fledged, or left the nest, a few weeks ago). As well, cam viewers have observed several late-night fly-bys and attempted attacks on the Osprey chicks, by what look to be owls or some other raptor.


While this predation is hard to watch, it’s important to remember that predation is a natural part of the animal word—both Osprey and Great Horned Owls are raptors, hunters who eat other creatures in order to survive. ORI would not normally have intervened if the chicks were being attacked by Great Horned Owls. We made the decision to intervene because of the baling twine, a human-caused situation.


 

What can you do to prevent Osprey from picking up baling twine?

Unfortunately, it’s hard to convince Osprey that baling twine doesn’t make for good nest material (believe us, we’ve tried!).


Two osprey chicks in a nest after the baling twine has been removed.
The two osprey chicks in the nest after the first baling twine removal. In the foreground is the osprey nest, a large circular shallow nest made of medium-sized sticks and lined with grasses. The two chicks are in the upper right side of the nest. Behind and below the nest is a view of a large pond, and beyond that open grasslands and the Mission mountains.

However, there are a few other things we can do to help make the world safer for osprey and their chicks:


Pick up baling twine and other trash (such as fishing line), especially along rivers, lakes, and in fields