Peregrine Falcon (Falco peregrinus)
Associated Species: Other species that may use habitat in a similar way and/or respond similarly
to threats, management, and conservation activities include Golden Eagle, Prairie Falcon, Great
Horned Owl, Black Swift, and Common Raven.
Distribution: Peregrine Falcons have a more extensive worldwide range than any other bird:
they occur on all continents except Antarctica (Kingery 1998). They breed across the North
American Arctic and southward along the Pacific Coast, through the Rocky Mountains, and in
scattered locations in the eastern U.S. Peregrines breed along the foothills in Physiographic Area
62 and at scattered locations in the higher mountains. About one-fourth of Colorado's peregrines
nest in the region. Statewide in 1998, CDOW personnel found peregrines occupying 90 of 107
known nesting sites and located six new sites. Seventy-six of the sites were occupied by adult
breeding pairs which produced 157 young.
Habitat Requirements: In Colorado, Peregrine Falcons breed on cliffs and rock outcrops from
1370 m to more than 2740 m (4,500-9000 ft) in elevation. They most commonly choose cliffs
that lie within pinyon-juniper and ponderosa pine zones, but this choice probably depends on the
nature and location of the cliffs rather than an attraction to these habitats. They select a ledge that
has a wide view and plentiful prey in the area. Most eyries (nest sites) are within a mile of water.
The falcons hunt in adjacent open meadows, forested tree top areas, around lakes and rivers, and
shrubsteppe. Early records suggest that they once nested in somewhat more accessible spots, but
now they tend choose cliffs higher than 60 m (200 ft) in undisturbed areas. Recovery efforts have
also succeeded in coaxing them to nest on tall buildings in urban areas where they subsist largely
on Rock Doves.
Ecology: Some Peregrine Falcons reside in their territories in Colorado throughout the year, but
most winter south of Colorado and arrive on the breeding grounds in March. They immediately
begin courtship activities and are laying eggs in April. The eyrie is a level ledge beneath an
overhang where they can scrape a depression in debris. Eggs hatch after a 32-35 day incubation
period and the young remain on the nest for another 39-46 days. The young remain dependent
on the parents for another period of 30 days or more until dispersing in August and September.
They winter in Mexico, Central and South America. These falcons feed on smaller birds almost
exclusively, with White-throated Swifts and Rock Doves being among their favored prey. They
have been known to take bats in the early morning or late in the day when bats become active.
Management Issues and Conservation Recommendations: Disturbance from recreational
activities (rock climbing and hiking) can cause nest failure. Identify nest sites and restrict
recreational activities during the nesting period. This may require seasonal closures or
rerouting of some hiking trails around the base or top of some cliffs during the breeding season.
Establish buffer zones to minimize conflicts around nesting sites, especially if the cliff is a
popular destination point for hikers or rock climbers. Establish Research Natural Areas, Areas
of Critical Environmental Concern, Special Management areas, Important Bird Areas, or
sanctuaries where appropriate to protect eyries.
Urbanization has encroached on some feeding territories, resulting in abandonment of traditional
breeding sites. Determine if roads, housing developments, or other human related activities have
a negative impact on nesting or foraging habitat.
Most of the known nest sites in Colorado are on public lands administered by the Bureau of Land
Management, U.S. Forest Service, and National Park Service. Coordination with land managers
is imperative in protecting nest sites.
In the 1980s there were still occasionally White-throated Swift and swallow die-offs in western
Colorado and eastern Utah due to pesticide poisoning (J. Connor, National Park Service, personal
observation). Many birds that migrate are still subjected to chemical exposure especially around
agricultural fields. In the United States, DDT caused the near extinction of the Peregrine Falcon
in the 1950s and 1960s, and pesticides are still a serious threat to birds in the late 1990s. Monitor
Peregrine Falcons and their habitat for herbicides, pesticides, and other chemicals that would
have a direct or indirect impact on them. Research Peregrine Falcon food sources for pesticide
and herbicide poisoning. Research threats to food in Peregrine Falcon winter habitat.
Status and Reasons for Concern: This species occupies a unique habitat type (cliff/rock) in this
physiographic area. It was delisted from the Federal Threatened and Endangered Species list in
1999. Monitoring protocols call for the peregrines to be monitored for at least the next 13 years
(2012) to ensure that 100 to120 breeding pairs are maintained in Colorado (Gray 1995). Within
the cliff/rock habitat in Physiographic Area 62, BBS data collected between 1969 and 1996 are
too sparse to allow analysis of trend data. This species is monitored by CDOW.
Biological Objective: Maintain or increase the species' distribution and abundance, based upon
results from the CDOW monitoring program. Maintain current breeding densities at all known
nest sites, and improve breeding densities by protecting these sites from human disturbance.
Continue to monitor known breeding sites and survey other potential nest sites with the state.
Selected References: Andrews and Righter 1992, Gray 1995, Kingery 1998.