We compared 50-m fixed-radius point-count detections for four bird species with density data from spot-mapping in order to evaluate the relationship between monitoring methodologies. We conducted this study in five Missouri oak-hickory forest study sites over eight years. There were significant positive correlations between monitoring methods, but the strength of these relationships varied for Acadian Flycatchers (Empidonax virescens), Ovenbirds (Seiurus aurocapilla), Worm-eating Warblers (Helmitheros vermivorus), and Wood Thrushes (Hylocichla mustelina). There was significant bias associated with the point-count detections for Acadian Flycatchers, Worm-eating Warblers, and Wood Thrushes. The direction and degree of bias varied; for example, Acadian Flycatchers and Worm-eating Warblers were on average significantly overestimated by point counts, whereas the Wood Thrush was significantly underestimated and Ovenbirds were slightly underestimated. The magnitude and direction of the bias error varied with spot-map density estimates of the species, but was not related to specific study sites or years. Thus 50-m radius fixed-radius point counts appear to reflect general density trends for the four species, especially for Ovenbirds, but there are also density related biases associated with point-count detections.
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Vol. 75 • No. 2