An average osprey nest near Missoula contains a quarter mile of bailing twine, an amount that kills 10 percent of osprey chicks, according to University of Montana researchers.
Photo by Chad Harder
Erick Greene expected a fairly standard outcome when he arrived at a ranch outside Deer Lodge in late July: Knock on the rancher’s door, explain the plan to leg-band and gather samples from the osprey chicks in a nearby nest, and move on. But seeing the long tresses of bailing twine hanging beneath the nest, the University of Montana researcher decided to spend a little more time with the rancher.
Greene, a bird biologist, explained that polypropylene bailing twine, which is used by ranchers during haying operations, is extremely strong and prone to tangle, a deadly combination for osprey. He then invited the ranchers to join him in the “bucket truck” to observe the lofty nest first-hand. What they found were two young chicks, and then a tattered ball of orange twine with a fledgling beak poking out from its center. A third chick was completely snarled in string.
“There was just this little head sticking out,” says Greene. “It didn’t look good.”
Greene works with Heiko Langner, an assistant research professor at UM, and Rob Domenech, director of Raptor View Research Institute, to study osprey along the Clark Fork
River from Anaconda to Frenchtown. As part of recently concluded three-year project, the group had originally tested the birds’ blood for the “Big Five” toxins—arsenic, zinc, lead, cadmium and copper.
“Osprey chicks reflect the contaminants of the river,” says Langner. “From the time they hatch to the time they fledge, osprey chicks only eat fish from a three- to four-mile stretch of river.”
Capitalizing on this localized feeding pattern, researchers could use osprey blood to identify localized “hot” stretches of the Clark Fork River during its ongoing cleanup.
But the researchers ended up finding low levels of the “Big Five.” Instead, mercury levels were soaring, and in some cases off the charts. At the time of this discovery last year—widely reported in the media, including the Indy—the researchers believed this was why the 20-30 known active nests near Missoula had dwindled to four or five. But mercury isn’t the only thing killing the birds.
“Bailing twine kills lots more chicks than mercury,” says Greene, who has studied birds for 25 years. In three years of monitoring 200 nests, Greene says he’s seen multiple chicks get tangled in the twine, and now encourages ranchers to never leave leftover cord in the field.
Greene says the average nest monitored by researchers contains about a quarter mile of twine, a problem that kills 10 percent of osprey chicks. Langner says after scavenging twine from just three nests earlier this year, he ran out of room in his trunk. Adult osprey also fall prey to the string, and during the project researchers found multiple adults dead, dangling in twine.
Luckily, that wasn’t the case with the balled-up bird near Deer Lodge. After cutting the twine from the chick, Greene realized that an infection had enlarged one leg to double or triple its normal size. After some “minor surgery” they returned it to its nest. The event made quite an impression on the ranchers.
“They had always seen bailing twine in their nests,” says Langner. “They just never thought how dangerous it could be. Now they will never leave bailing twine in their fields.”
One week later, Greene returned to check on the chick.
“I was pretty sure there’d be just two, but there were three healthy chicks staring at us, and even after I picked them up I couldn’t tell which was which,” he says. “I had to read the band number to figure out which one it was.
“If we’d have gotten there a day later,” he continues, “I don’t think it would have made it. It’s neat to have the ranchers get to see that, and I think they’ll get the word out to their neighbors.”
That will be an important step because while twine can be easily cleaned up, mercury can’t. The researchers recently secured new funding which will enable them to continue monitoring the health of local raptors, the Clark Fork River and its Superfund-designated cleanup.
“Whatever we’re finding should be of concern to people, especially those eating fish from the Clark Fork,” says Greene. “Osprey are really good environmental canaries.”