Hunting Tactics of Peregrines and other Falcons

There is a foreword and abstract in Dutch (as well as English versions) and chapter 15 is also in Dutch with an English abstract.

This dissertation describes the foraging habits and capture rates of four species of bird-hunting falcons; Peregrine (Falco peregrinus), Merlin (Falco columbarius), Gyrfalcon (Falco rusticolus), and Prairie Falcon (Falco mexicanus). Eight of the nine study areas were situated in western Canada in widely different habitats, and the observation periods intermittently included all seasons over 44 years, 1965-2008. The various chapters report and compare the location-specific hunting methods and choice of prey of these falcons in the following scenarios: (1) Migrating Peregrines hunting waterbirds at Beaverhills Lake, a large wetland in central Alberta; (2) Migrating Peregrines and Merlins capturing small shore-birds and passerines at Beaverhills Lake; (3) Breeding Peregrines that launched their hunts from the high chimneys of an industrial powerplant by a large Alberta lake and selectively took gulls; (4) Marine Peregrines nesting on Pacific island cliffs and preying on seabirds; (5) Peregrines and other raptors hunting wintering Dunlins (Calidris alpina) and ducks at Boundary Bay on the Pacific coast of British Columbia; (6) Peregrines specializing on teal and American Wigeon (Anas Americana) wintering on coastal farmlands; (7) Territorial pairs of Peregrines and Prairie Falcons competing for prey and nest sites on a sympatric breeding range along an Alberta river; (8) Prairie Falcons and Gyr-falcons wintering in the city of Edmonton and capturing Rock Doves (Columba livia); (9) Gyrfalcons hunting Mallards (Anas platyrhynchos) wintering on Alberta farmlands; (10) Klepto-parasitic interference from eagles and buteo hawks with hunting Peregrines and Gyrfalcons, and intra- and interspecific prey theft between falcons. The largest set of data pertains to the Peregrine, which was studied in all seasons and habitats except during winter in central Alberta.



In addition, this thesis reports on the population dynamics and nest site competition between Peregrines and Prairie Falcons on a sympatric breeding range in Alberta over a span of 48 years. The Peregrine became extirpated during the 1960s. Large-scale efforts to reintroduce the species in the 1990s seemed initially successful, resulting in seven new breeding pairs, but they dwindled to one, while the Prairie Falcons continued to do well.



The first chapter of the thesis details 15 years of Peregrine migrations at a large lake in central Alberta, and the last chapter analyses the fall passage and hunting habits of Peregrines along the Wadden Sea coast of the Netherlands. There, the specific research question was whether or not Dunlins wintering on the Dutch coast would engage in over-ocean flocking manoeuvres during high tides that inundate all mudflat habitats. The phenomenon proved to be very rare and the probable reasons are discussed in detail.