Numerous cliffs in the Flatirons are closed each year to allow cliff dwelling wildlife a chance to reproduce undisturbed. Seasonal closures are generally in effect from February 1 – July 31 to protect nesting and roosting sites of eagles, falcons and osprey. These areas are monitored for nesting activity, and closures may change. For a complete list of closures and the most up to date information, visit the Open Space and Mountain Parks website or call 303/441-3440. Closures in Boulder Canyon also occur during the same time frame, please see the Forest Service’s website for details.
Please be aware that it is against federal, state and municipal law to disturb any nesting bird of prey. It is also against municipal law to enter any closed area.
Why are Climbing Restrictions Necessary?
Raptor species such as the peregrine falcon (Falco Peregrinus) are recovering from the effects of pesticides (most notably DDT) in the food web in the 1960s. This means the status of the population is changing; falcons are returning to historic nest sites where they have been absent for over two decades and expanding their range into new areas. Seasonal climbing restrictions to protect cliff-nesting raptors, including closing portions of cliffs, have been implemented since the 1970s in numerous areas around the country. Over half of the restrictions listed each year are for peregrine falcons, but they also apply to nesting prairie falcons and golden eagles. All these birds are protected at the federal and state level.
How Climber Disturbances Impact Raptors
Climbing activity can impact raptor nests by 1) altering the habitats (foraging, nesting, roosting) in which they live, and 2) disrupting foraging, nesting, and roosting behavior. The presence of a person near an active nest site can cause disruption to normal behavior in the case of particularly sensitive birds. Interference with normal feeding activities and raptors taking avoidance flights will decrease birds’ energy intake levels, which may affect overall breeding success. Rock climbing can be a source of disturbance if it occurs in close proximity to the nest. Unlike other forms of disturbance caused by land users such as hikers, a climbing party may be on the rock face for longer periods of time, and may come in much closer proximity to the nest.
Because few scientific studies exist that specifically relate to recreation disturbance and its impact on cliff-nesting raptors (and none relate to climbing) land managers often take a conservation approach in establishing seasonal restrictions (in terms of the size and scope of the closure.) Resource managers and biologists have little data on which to base seasonal raptor restriction decisions. This has led to substantial discrepancies across the country on the criteria for which restrictions are made.