Peregrine Falcon Scrape Site Selection

Hi All,
Bruce Connery of the National Park Service has contributed this informative blog about falcon nest site selection.
Enjoy!
All the Best,
Patrick Keenan
BioDiversity Research Institute


Peregrine Falcon Scrape Site Selection

The selection of a scrape, or nest site, for peregrine falcons occurs in tandem with other courtship activities and behaviors. The adults may visit several likely suitable ledges or structural platforms in the weeks leading up to the eggs being laid, seeking sites that have the right combination of factors such as aspect, exposure, and protection. Along with courtship activities such as pair flying and food exchanges, the adults often engage in ledge or scrape displays. These displays further strengthen the bond between the pair and also indicate possible nesting sites.

Falcons prefer scrapes that are composed of pea-sized gravels with small grains of sand or gravel and some soil, but where precipitation can drain away from the eggs, incubating adult, and eventually the chicks. Falcon scrapes may occur on natural or artificial structures but must be inaccessible from terrestrial predators and are often situated between vertical faces or walls above and below the scrape.

Natural candidate nesting sites can be open exposed ledges, ledges under an overhanging cliff, or raptor stick nests that the falcons claim for themselves from other raptors or from ravens that have an east to southern aspect. Scrapes on southeastern aspects provide morning warmth while protecting the adults and chicks from the hot mid- to late afternoon daytime temperatures that become common in late spring and early summer.

Artificial nest sites have good visibility and access and some protection from the sun and weather. Artificial sites may be the tops of bridge supports or structures, tops of buildings or on towers used in manufacturing complexes, but again must have a granular substrate that the adults can move around or hollow out into a depression to hold the eggs.

Nest boxes are often placed on towers, bridges, or other high locations were falcons have been observed at least perching and resting. The boxes can vary in size according to the dimension of the location they were they will be placed, however they must have sides that rise above and hold the granular substrate and have good drainage.

Bruce Connery
Biologist
National Park Service