An analysis of use of nest boxes by mountain bluebirds in southwestern Manitoba

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Munro, Hugh L.
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Surface cover types and nest box properties characteristic of nest sites used and not used by mountain bluebirds nesting in southwestern Manitoba were investigated. Twenty-six variables considered pertinent to secondary cavity nesting passerines were evaluated at 1169 nest boxes on 28 nest box lines in 1980. Stepwise discriminant function analysis was used to determine which variables were important in discriminating between nest sites used and not used in 1) the first nesting period and 2) both nesting periods of mountain bluebirds. Variables unsuitable for inclusion in discriminant analysis were analyzed by chi-square criteria. Nest sites were used in a variety of habitats, but were associated positively with grass and wooded pasture and negatively with shrub pasture, long grass, and fallow field... Distance to the nearest building, entrance hole diameter, both depth, and line age were the important discriminating variables when nest box properties were analyzed separately. Nest box properties were superior to surface cover characterisitics in separating used and unused sites... Entrance hole orientation, directional location of the nest box from the road, type of supporting structure, box condition, and land use and disturbance in the vicinity of the nest box had no impact on use by mountain bluebirds... My analyses reveal that mountain bluebirds are euryvalent in their use of breeding sites, but appear to prefer grass and wooded pasture and avoid shrub pasture and heavily cultivated areas. Characteristics of the nest box are more operative than surface cover characteristics in determining use by this species.