Hungry eagle foils heron recovery near Rio Grande Trail
PITKIN COUNTY – Just when it looked like a great blue heron colony was going to be re-established in the midvalley this spring, a golden eagle turned a nursery into a buffet.
The eagle devoured heron chicks and eggs from six nests on Rock Bottom Ranch, near Basalt, between May 28 and June 6, according to Mary Harris, a resident of the area and avid bird watcher.
“He just gobbled up everything,” she said.
While it is easy to write off the attack as an act of nature, the timing couldn’t be worse. The nesting areas at Rock Bottom Ranch, after consistent use as a rookery in the spring, have been abandoned in recent years. Wildlife enthusiasts contend that the opening of the Rio Grande Trail has contributed to the flight of the herons. Critics have asked the Roaring Fork Transportation Authority to delay the opening of the trail until later in the spring. Currently, a 2 1⁄2-mile section of the trail is closed from Dec. 1 until May 1. That section is east of Catherine Store. RFTA’s board of directors decided to maintain the current closure and collect more data on wildlife use of the corridor.
Harris said cold and wet weather this May limited use of the trail, so the herons weren’t spooked from the site. That was important, she said, because once the chicks hatch, the adults will stay put.
Her neighbor, Jim Biebl, kept a log of heron activity this spring. On April 22, he observed five herons sitting on nests and 14 altogether hanging out in the Rock Bottom Ranch area. Males would catch fish and bring them back to the females on the nests, he said. Unlike the prior two years, the herons didn’t scram when the trail opened on May 1, and the number of nests with sitting herons grew to six.
Biebl said the first observed herons hatched on May 15. But the success story turned somewhat sour on May 28 when the Harrises and the Biebls noticed the adult herons were extremely agitated. The problem was obvious when the families observed the nesting grounds.
“It was a golden eagle chowing down on little herons and eggs,” Biebl said.
Although agitated, the adult herons did little to defend their territory or offspring. Ravens and osprey nesting in the area dive-bombed the eagle to try to drive it away, without success.
One of the rare defensive maneuvers by an adult heron was captured in a photo. Mary Harris and Jim’s daughter, Brittany, teamed on June 3 to take a picture of a heron trying to defend a nest. Mary said she put a digital camera to her telescopic lens while Brittany used another telescope to tell her when to take a photo. They hope to enter one of the best photos in an National Audubon Society contest.
Harris said the eagle kept returning to the colony and feasting on the eggs and chicks. It was like candy laid out for a kid, she said. The eagle scored its biggest haul Saturday, June 6, when it invaded a nest with four rapidly growing heron chicks. It killed and devoured all four, although some probably fell out of the nest while trying to escape, Biebl said.
With all the chicks dead and the eggs destroyed, the adults fled the area.
“Besides being really sad, it was really wild watching it,” said Biebl.
Harris agreed: “It was really exciting to watch all the action but sad, too. He just slowly picked off everything.”
The golden eagle’s behavior is extremely rare, research by both of the experienced bird watchers indicates. The birds stay in higher ground, Missouri Heights, for instance, and rarely patrol riparian areas in the valley floor. Harris, a member of the National Audubon Society, is attempting to find out from bird experts if they know of any similar situations. She and Biebl also found it strange that the herons did so little to protect their territory.
Harris said the incident stresses the need for humans to do what they can to assist development of heron rookeries. The birds aren’t endangered, and there are at least three other colonies in the Roaring Fork Valley. However, the Rock Bottom feeding frenzy shows that more rookeries are better for the herons.
“I just think the extermination of this nursery was a force of nature,” she said. “It’s important to protect fiercely what we do have.”
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