Nest site selection and coexistence in eastern and western kingbirds at Delta Marsh, Manitoba

Abstract

Characteristics of nest sites of eastern and western kingbirds on the forested ridge, Delta Marsh, Manitoba, were studied during 1976 and 1977. Habitat analysis was performed around each nest site at three levels of resolution: macrosite (.07 ha), microsite (.01 ha), and nest tree. Principal component analysis of overstory vegetation characteristics of randomly selected plots (.01 ha) defined the 'habitat space' of the study area in terms of the major components of variation in the vegetation. Discriminant function analysis of the random plots identified the major gradient in the variation of the vegetation (corresponding roughly to a microgeographical gradient from north to south), and characterized the differences between north- and south- zone type microhabitats. Principal component analysis of the vegetation characteristics of kingbird nest sites at both macrosite and microsite levels determined the relative position of each species in the 'habitat space'... A combination of macrosite and nest tree variables achieved the best statistical separation between eastern and western kingbird nest sites, using discriminant function analysis of the combined data sets. The degree of separation of the species along the resource dimension of nesting habitat, defined in terms of the best discriminating variables, is considered sufficient to permit coexistence of these species in the event nesting habitat should prove to be the resources limiting the population of either species.