Competition Between Mountain Bluebirds and Hairy Woodpeckers
Competition between Mountain Bluebirds and Hairy Woodpeckers.-The following observation of a pair of Hairy Woodpeckers (Dryobates villosus) and a pair of Mountain Bluebirds (Siuliu currucoides), in apparent competition for a nesting site occupied by the former, was made at Westwick Lake in the Cariboo region of British Columbia on June 3 and 5, 1937.
A female Mountain Bluebird was seen to enter and leave a hole in the trunk of a live aspen (Populus tremuloides), one of a group of these trees on open prairie near the lake shore. As I approached the tree, the unmistakable cries of young Hairy Woodpeckers were heard, and the origin of the sounds was definitely located as coming from the cavity into which the bluebird had disappeared. For the ensuing fifteen minutes or so the tree was watched closely from a distance of ten feet and this, briefly, is what happened: Every few minutes the male woodpecker entered the nest to feed the young on ants which he obtained from a near-by aspen. The female woodpecker did not appear. Meanwhile both the female bluebird and its mate remained in the vicinity and showed constant interest in the nest. Sometimes the female hovered in front of the entrance and she entered the nest four times with nesting material in her bill. The male bluebird continued in close attendance, flying from branches to branch above the nest entrance where several times it was joined by the female. During this time there was no show of hostility on the part of any of the three birds concerned.
Two days later the nest was under observation for half an hour. The young woodpeckers were still vocal and their cries increased whenever I walked to the foot of the tree. In the course of this half hour the female bluebird once hovered in front of the nest entrance and once, carrying a long straw in her bill, attempted unsuccessfully to enter. For the remainder of the time the pair of bluebirds moved about restlessly in the branches of the aspen. The parent woodpeckers did not appear until near the end of the period of watching.
Circumstances did not permit further observatiorr and the conclusion of the contest must remain in doubt. A somewhat similar incident has been reported by A. H. Miller (Auk, 52, 19353467-468). In this case there was competition between the same species for a newly excavated nest and the woodpeckers were dispossessed.-J. A. MIJNRO, Okanagan Landing, British Columbia, October 27, 1942,
