The peregrines reacted to calls and activity of nearby Raven pair; the female made a number of flight loops out and around area of Ravens and back to a ledge perch each time. No direct approach towards the Ravens, but a gentle and firm message of territorial warning!

According to Tom Cade’s proposed model, with nesting cliff as center: there are a series of threshold perimeters surround eyrie with decreasing defense as distance from eyrie increases. Inner perimeter may be only 200 m; within that, attacks always occur. In outer perimeter, attacks only occur over food or favored perches.

The peregrines may be seen making flight patrols of area around nesting cliff.  This may take place when adults fly along cliff face or top to a given distance, turn, and repeat course, frequently in seemingly relaxed, but intentional flight. Often intruders, including Ravens, Red-tailed Hawks, and others are stooped at, sometimes jointly by pair, and loud, assertive cack calls are given.  The message of territorial boundaries is being conveyed loud and clear!

Literature cited:

White, Clayton M., Nancy J. Clum, Tom J. Cade and W. Grainger Hunt. 2002. Peregrine Falcon (Falco peregrinus), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA. https://doi.org/10.2173/bna.660