By Dana Bove, Diane Kristoff, Holly Anderson, Anita Langdon and Theo Kuhn
The nesting bald eagles at the Carolyn Holmberg Preserve on Boulder County Open Space are nearing the end of a successful breeding season, rearing three healthy eagles. Two remaining juvenile fledgling eagles are still in the critical period of post-fledging dependence (PFD) but nearing dispersal from their parents’ territory. The PFD nesting period is vital for these juvenile eagles to obtain requisite fitness, flight and nascent hunting skills for optimum chances of survival after dispersal. Studies by Front Range Nesting Bald Eagle Studies (FRNBES) on 34 fledgling juveniles, document that nearly all the prey during this key period is still provided by their parents.
Beginning August 6th, Boulder County Parks and Open Space (BCPOS) plans to re-open an 800-meter-long trail to bikes and pedestrians, which will encroach within 30-50 meters of the most utilized habitat for these juvenile and adult eagles. Two juveniles remain within this protected habitat and are still fed daily by their parents. The next week under their parents’ loosening oversight will allow more honing of flight and survival skills prior to dispersal. Many studies have found that first-year survival rates for juvenile eagles after dispersal can be as low as 50%, all of which is highly dependent on the fitness and early skills acquired during the brief PFD period.
Nearly 60% of the Holmberg Preserve is dedicated for agricultural use, whereas less than 4% of these 1200 acres are intensively utilized and vital to these territorial eagles. FRNBES refers to this 800-meter-long trail as the “Cutoff Trail” as it affords no commuting or other meaningful advantage to trail users. Yet, whether or not these fledgling and adult eagles continue to use this territorial habitat — and despite a high likelihood of disturbance by trail users — BCPOS remains committed to an August 6th trail opening.
A similar management style is reflected in BCPOS’s insistence that a one-acre riparian area within one-third of a mile of the Stearns Lake eagles’ nest site must remain open “to balance the public access for fishing.” Yet nearly 56% of the Stearns Lake shoreline is open already to public fishing. Allowing that additional acre yields a de minimis benefit to anglers, while associated human encroachment has been demonstrated by FRNBES to restrict usage and hunting opportunities by the Stearns eagles in this key habitat.
A petition by multiple conservation groups and nearly 250 citizens requested that the county permanently close the “Cutoff Trail.” The petition reminded us that Holmberg is a preserve that has a written goal of first protecting wildlife. FRNBES shared video and other details of disturbance with the county documenting the entire family of eagles flushed repeatedly last summer by agricultural tenants along the “Cutoff Trail.” Over the last few years, the Stearns eagles have been twice displaced from their original nest site due to human development.
We continue to ask ourselves and others what promotes such management at BCPOS that in 2020 spurred this statement to BCPOS from County Commissioner Matt Jones at the final Holmberg Planning meeting: “Where does the balance come in with the wildlife and the ecology? When I look at all this laid out, it seems to be a secondary consideration … this is a preserve, and we should treat it as such. We can have recreation in there, but it should be secondary to protecting the resource.”
With respect to BCPOS management of bald eagles, we advise a closer look at their own senior wildlife management’s statements to their advisory board members, “bald eagles are generalists, who are making their living by taking other’s prey and putting pressure on other raptors, and making life hard on others” and “we have a new landscape out there, they are generalists, and they just keep coming.” Or perhaps a comparison in a recent Colorado Sun Article by an “unidentified” local land manager comparing bald eagles to seagulls.
The current plan to open a non-requisite trail in the waning period of post-fledging dependence will cause stress and disruption to the juvenile and adult eagles by human encroachment. For the protection of the eagles and their future at the Holmberg Preserve, please immediately let BCPOS management and the county commissioners know that this trail must remain closed.
Dana Bove, Diane Kristoff, Holly Anderson, Anita Langdon and Theo Kuhn are members of Front Range Nesting Bald Eagle Studies.
