Tree-Nesting Peregrine Falcons in British Columbia

Abstract

Records of Peregrine Falcons (Falco peregrinus) nesting in trees, either in nests built by other large birds or in hollow tree trunks, have been well documented in parts of the Old World (Thomasson 1947, Dement'ev and Gladkov 1951, Fischer 1968, Mebs 1969). In North America, a few such records are available from Alaska and the central United States, but the details are obscure (Hickey and Anderson 1969). This paper provides information on six tree aeries located on offshore islands, found during a survey of seabird nesting colonies along the northern coast of British Columbia in June and early July 1976. Because of the peregrine's sensitivity to human disturbance and because of recent public concern for the species, we do not give exact aerie locations but have filed them (see Campbell and Stirling 1971) with the British Columbia Provincial Museum (BCPM). We discovered the first tree nest of peregrines on 20 June. While searching through dense undergrowth along the shores of a small wooded island for nesting alcids, we encountered an agitated adult female peregrine calling from the top of a dead Sitka spruce (Picea sitchensis). The shore sloped gently towards the sea. Few cliff ledges were available for nesting falcons, but two abandoned Bald Eagle (Haliaeetus leucocephalus) nests, about 25 m apart and 34 m from shore, were present near the top of the island. In one nest, about 18 m above ground, a large, white, downy, young falcon sat near its edge. We could not reach the aerie (BCPM Photo No. 454) so exact nest contents were not determined although we did not observe other nestling activity. Prey remains below the nest included Rhinoceros Auklet (Cerorhinca monocerata), Cassin's Auklet (Ptychoramphus aleuticus), and Pigeon Guillemot (Cepphus columba), none of which nested on the island. The nearest seabird colony (storm petrels and auklets) was about 100 km to the SE.