Resident ospreys “Rainbow” and “Shadow” have escaped the winter cold for warmer climates, and their travels are teaching Coloradans heaps about the birds’ behavior.
Named for their summer nesting sites on Rainbow Bay at Lake Granby and the shore of Shadow Mountain Reservoir, the adult ospreys were outfitted with solar-powered satellite tracking units last June. The units are like bird-sized backpacks, and provide daily updates on their location. The monitoring is a joint effort between the U.S. Forest Service, Rocky Mountain National Park and the Rocky Mountain Bird Observatory.
“Understanding the full-life cycle of migratory birds helps identify conservation needs,” stated Kyle Patterson, with Rocky Mountain National Park, in a press release.
According to Patterson, the information will help biologists learn about the birds’ migration routes, stopover sites and winter ranges. The data will help coordination efforts with landowners to protect the species. As the team tracks the birds for the next two to three years, they’re posting their geo-locations online in an effort to help educate the public as well.
“It’s just the coolest thing. We’re learning so much,” said Doreen Sumerlin, wildlife biologist with the U.S. Forest Service Sulphur Ranger District in Granby.
While similar studies have been conducted on osprey in other states, both Patterson and Sumerlin said this is the first time geolocators have tracked osprey in Colorado. Patterson also said it’s the first time both a geolocater and satellite transmitter have been used on any migratory bird to compare the technologies.
Scientists with the U.S. Forest Service coordinated with those at the Rocky Mountain Bird Observatory and Rocky Mountain National Park to determine when to capture the birds and fit them with their trackers.
“Time was of the essence,” Sumerlin said. “We wanted to do it while the birds were still on their eggs or the chicks were very young, so the chicks wouldn’t be startled and jump from nest.”
MPE linemen pitch in
The bird biologists had help from Mountain Parks Electric, one of the only local crews with equipment capable of reaching nesting ospreys. The birds build their nests as high as possible, often on poles Mountain Parks Electric staff constructed to keep them off power lines.
The Mountain Parks Electric linemen held shade cards to protect the eggs and chicks while biologists worked to get the trackers on their mothers.
“We prepared in advance to protect those really small chicks and unhatched eggs,” Sumerlin said. “They’re vulnerable to overheating by the sun when the mother isn’t there to incubate them.”
It’s common for ospreys to lay three eggs and successfully fledge two young. Rainbow hatched and raised two chicks, while Shadow fledged all three of her eggs. Sumerlin attributes the mothers’ success, in part, to the diligent shading by Mountain Parks staff.
The trackers showed the mothers rarely left their nests until the chicks matured and became independent. Then, both Shadow and Rainbow started making short foray trips, flying to Hot Sulphur Springs or Fraser, then returning to the nest. Sumerlin figures the birds were building strength for their big migration south.
“We can only guess what they’re doing, but it’ makes sense,” she said. “It’s like training for a marathon after sitting on the couch for three months, it’d be really hard.”
The osprey began surprising biologists as soon as they set off for their migration, crossing the Continental Divide near Berthoud Pass and cruising down the Front Range. This meant the birds immediately jumped from the Pacific Flyway to the Central Flyway that follows the Great Plains.
“The assumption was that birds would migrate in the flyway they’re in, but the first thing they did was leave,” Sumerlin said. “None of us expected that.”
The birds didn’t travel together, but followed roughly the same migratory path. They cruised down the Front Range, then followed the Arkansas River. They made an abrupt turn near the panhandle of Oklahoma, then jetted south in a near-straight line through Texas into Mexico.
Shadow dove down the length of Texas, taking just three days to cross the state. She’s settled in a wetlands area on the Gulf Coast, right near the Texas-Mexico border.
Rainbow is wintering among the orchards and agricultural land along the Tampaón River, about a 60-mile flight from the shipping town of Tampico and a 170-mile flight south to Mexico City.
“We don’t know if they’re there individually or if they’re with other birds,” Sumerlin said. “I’d love to go down there and follow them around to see what they’re doing.”
Sumerlin said the fish-loving birds are likely resting and fattening up after their 1,300 to 1,700-mile journeys and preparing for the return flight north.
Barring any catastrophe, osprey return to their nests each year, so Grand County residents can expect to see Rainbow and Shadow back at their summer homes again this spring.
Over the next few years, the U.S. Forest Service, Rocky Mountain National Park and the Rocky Mountain Bird Observatory will continue using the tracked birds to educate local students and the public about the birds and migration. Sumerlin’s looking forward to seeing their return path home.
“I don’t know if they’ll follow the same route back or a different one,” she said. “I can’t wait to get that information.”
Leia Larsen can be reached at 970-887-3334 ext. 19603.
“It’s just the coolest thing. We’re learning so much.”
Wildlife biologist, U.S. Forest Service Sulphur Ranger District, Granby