Colorado Parks and Wildlife (CPW) along with numerous project partners have embarked on a four-year study to help better understand current population trends, habitat use and impacts of human disturbance on bald eagles along the state’s most densely populated corridor.
The Front Range corridor of northern Colorado is an area that is experiencing rapid human population growth — up 18 percent since 2000. Amazingly, this densely developed area also contains a high concentration of bald eagles. In CPW’s raptor-nest database, as of 2020, there were more than 90 breeding pairs of bald eagles in this corridor from the Denver metro area to the Wyoming state line.
“The reason we are focused on this area is the concentration of bald eagles along the Front Range, juxtaposed with the concentration of humans and human infrastructure along the Front Range,” said CPW Avian Researcher Reesa Conrey.
Populations of the American bald eagle — the bold national symbol of the United States — have quadrupled since 2009, according to a new report by the U.S. Fish and Wildlife Service and its partners. However, eagles did not always thrive in this urban corridor. By the end of the 1970s there were only three known bald eagle nests in Colorado with none on the Front Range. Bald eagle populations declined in the early- to mid-20th century due to pesticides (primarily DDT), human disturbance, land conversion and loss of trees for nesting habitat.
Thanks to protections implemented for the species and DDT being banned for general use back in 1972, the slow recovery process started. In Colorado, that rebound has accelerated over the past few decades, concurrent with human population growth along the Front Range. The bald eagle was delisted from Endangered Species Act protection in 2007, although they still are protected by the U.S. Fish and Wildlife Service under both the Migratory Bird Treaty Act and the Bald and Golden Eagle Protection Act. CPW classifies the bald eagle as a Tier 2 “Species of Greatest Conservation Need.”
NEW RESEARCH PROJECT
Researchers, biologists and volunteers from CPW, the U.S. Fish and Wildlife Service, the Bird Conservancy of the Rockies (BCR), along with numerous city and county agencies have been working together for years to monitor Colorado’s bald eagles to better understand their environmental needs and disturbance tolerances. These partners are coming together to help with this new research project that launched in the second half of 2020 and is expected to have management implications to help conserve bald eagles in a region that will continue to see rapid human development and land use conversions.
The study is expected to last four years and will be the most comprehensive bald eagle monitoring project ever done by CPW.
“We are looking at nest sites along a gradient of human activities and disturbances from urban to rural areas,” Conrey said.
Researchers will mark a sample of bald eagles nesting along the northern Front Range with GPS-GSM transmitters. The transmitter data will allow them to intensively monitor habitat use and eagle movements year-round, during both the breeding and nonbreeding seasons. At the same time, staff and a large number of dedicated volunteers will continue to monitor reproductive effort and success by conducting observations at nest sites. As of July 2021, they have tagged seven eagles.
“The transmitters that we are using for this project are different from what typically have been used,” said CPW Avian Researcher Reesa Conrey. “Previous generations of wildlife transmitters required biologists to use antennae to pick up the signals or they connected to satellite networks. But these transmitters connect to the cellular communications network. It allows our transmitters to be lighter in weight. That reduces potential stress on the eagles and it was a good choice for us in the Front Range because we have a lot of cell towers in this area.”
VOLUNTEER & VIEWING OPPORTUNITIES
Bird Conservancy of the Rockies
BCR’s Bald Eagle Watch (BEW) program has a volunteer citizen science network that monitors nesting bald eagles along the Front Range and elsewhere. The program has been steadily increasing its number of citizen volunteers as well as its scope and intensity of monitoring. They are CPW’s major partner on the project and their volunteers are monitoring most of the nests in the project area and providing data for the project.
You can also just enjoy watching them, such as those in LaVern M Johnson Park, along the cliffs. Get out and view your local bald eagles in winter (when we have both resident and wintering birds) or spring/summer by using binoculars or spotting scope to keep your distance and keep the birds safe. If a bird modifies its behavior in response to you, then you are too close.
CPW is an enterprise agency, relying primarily on license sales, state parks fees and registration fees to support its operations, including: 42 state parks and more than 350 wildlife areas covering approximately 900,000 acres, management of fishing and hunting, wildlife watching, camping, motorized and non-motorized trails, boating and outdoor education. CPW’s work contributes approximately $6 billion in total economic impact annually throughout Colorado.