Birds thrive at Glenwood Springs quarry site, city survey finds

A Golden Eagle coming in to land on a rock in the mountains.
Getty Images/Stuartb

The nearby quarry site is an important habitat for predators, elk, and an impressive variety of birds, according to a report on the ecology of proposed quarry expansion site.

As the final report from the Colorado Natural Heritage Program at Colorado State University puts it, the proposed quarry expansion site is a high-quality natural habitat, which are increasingly altered by human activity.

“(This) site continues to provide high-quality wildlife habitat and is consequently important to the survivability of numerous native wildlife species,” said the report, which was commissioned by Glenwood Springs.

For one of the ecologists, a big surprise was the prodigious bird presence in the proposed footprint of the limestone quarry owned by Rocky Mountain Industrials (the name was changed from RMR Industrials, Inc., in January).

“It was a surprise to me to find so many bird species breeding on that small hill, further indicating the importance of that hill slope to a whole gamut of native wildlife,” said ecologist and botanist Delia Malone, one of the authors of the report.

In two surveys of the proposed new quarry boundary 2018 and 2019, the field team spotted 56 separate species of birds, either nesting, singing or flying over the site.

“Birds are really good indicators of how healthy, or how undisturbed a habitat is,” Malone said.

The surveyors spotted three golden eagles, a species on the state’s highest priority conservation list, flying over the site on 3 of the 5 observation days. They did not locate the eagles’ nest, but noted that the “cliff outcrops throughout the site provide potential golden eagle nest habitat.”

The ecologists reported spotting six other species on the state’s second-highest conservation priority list.

Commissioned by Glenwood Springs, the survey shows the importance of protecting the site, according to City Manager Debra Figueroa.

“Not only will the quarry have enormous impacts on our local economy, it will also have irrevocable impacts on the plants and wildlife that also call this area home,” Figueroa said.

Only one of those bird species, the Virginia’s warbler, was observed by ERO Resources Corp., the Denver-based consultancy RMI hired to survey the site in 2017 and 2018.

Edge effect

Beyond the birds, the 447-acre proposed quarry expansion on Bureau of Land Management land also serves as a spot that is relatively untouched by human activity despite its closeness to a population center.

Among the other species identified by the CSU team was a rare plant species known as silverleaf milkvetch.

The survey concluded that the “habitat throughout the survey site is a complex mosaic of plant communities which provide important ecosystem functions essential to the viability of native wildlife populations.”

It’s also a migration route for elk, deer and bighorn sheep. A herd of bighorn sheep have habitat east and south of the quarry site, and rut at the abandoned quarry site southeast of the proposed RMI expansion. Carnivores such as bobcats and mountain lions have been observed at the site.

Colorado Parks and Wildlife also identified the northern edge of the proposed quarry boundary as potential Canada lynx habitat.

The effects of expanding operations would extend beyond the quarry site, according to Malone.

“Environmental impacts extend well beyond the edge of the quarry hundreds of meters,” according to Malone.

Research indicates that the effects of quarrying rock extend up to 250 meters beyond the boundary of the site, Malone said.

“That habitat is altered. It gets hotter, it gets drier, and it gets windier,” she said.


The ERO field team found eggshells from an active Cooper’s hawk nest, and abandoned red-tailed hawk nests, as well as four inactive nests on the western edge of the proposed quarry expansion.

ERO Resources Corp. recommended that, to protect raptor habitat, RMI hold off activities between Feb. 15 and July 15 each year to avoid disturbing nesting raptors.

RMI said it would not strip topsoil between Feb. 15 and July 15 according to the proposed plan of operations.

Prior to disturbing vegetation, a qualified biologist would survey the area, and “Should any active nests be found, the BLM will be consulted to determine the best course of action for properly handling the situation,” the plan states.

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