Models for guiding management of prairie bird habitat in northwestern North Dakota

With grassland bird populations in the Great Plains exhibiting steep declin es, grassland managers require information on bird habitat needs to optimal ly manage lands dedicated to wildlife. During 1993-1994, we measured bird o ccurrence and corresponding vegetation attributes on mixed-grass prairie in northwestern North Dakota. Three hundred and ten point-count locations ove r a wide range of successional stages were sampled. Ten grassland passerine species occurred commonly (i.e., at >10% of point count locations), includ ing two species endemic to the northern Great Plains [Baird's sparrow (Ammo dramus bairdii) and Sprague's pipit (Anthus spragueii)], and several specie s of management concern [bobolink (Dolichonyx oryzivorus), grasshopper spar row (Ammodramus savannarum), clay-colored sparrow (Spizella pallida)]. Some species were ubiquitous and had generalized habitat associations [e.g., sa vannah sparrow (Passerculus sandwichensis)]. Others exhibited more finely t uned, closely overlapping use of relatively short, sparse to moderately den se, grass- and forb-dominated habitat. We used logistic regression models t o predict bird species' occurrence based on nine vegetation variables. Prev iously undefined limits of vegetation height and density were identified fo r Baird's sparrow and Sprague's pipit, and of shrub, cover for Baird's spar row. Our findings underscore the need for a mosaic of successional types to maximize diversity of prairie bird species. Managers may reduce confusion created by generic treatment prescriptions for grasslands by focusing on ab solute rather than relative measures of vegetation, and by integrating stan dard data from multiple bird habitat studies across regions.