TL;DR: This paper used distance sampling with line transects to investigate differences in detection probabilities among observers and among three species of grassland songbirds: Henslow's Sparrow, Grasshopper Sparrow (A. savannarum), and Savannah Sparrow (Passerculus sandwichensis).
Abstract: Differences among observers in ability to detect and identify birds has been long recognized as a potential source of error when surveying terrestrial birds. However, few published studies address that issue in their methods or study design. We used distance sampling with line transects to investigate differences in detection probabilities among observers and among three species of grassland songbirds: Henslow's Sparrow (Ammodramus henslowii), Grasshopper Sparrow (A. savannarum), and Savannah Sparrow (Passerculus sandwichensis). Our review of 75 papers published in 1985–2001 found that the most commonly used methods were fixed-width transects (31%, 23 papers) and fixed-radius point counts (20%, 15 papers). The median half-width of fixed-width strip transects used by researchers was 50 m, but our results indicated detection probabilities were 25 m for most observers and species. Beyond 50 m from the transect line, we found that as many as 60% of birds were missed by observers an...
TL;DR: The authors investigated the association of grassland birds with field-and landscape-level habitat variables in south-central Wisconsin during 1985-1987 and found that only landscape variables were associated with the density of bobolink (Dolichonyx oryzivorus), eastern meadowlark (Sturnella magna) and all birds that were grassland species of management concern.
Abstract: We investigated the association of grassland birds with field- and landscape-level habitat variables in south-central Wisconsin during 1985–1987. Landscape-level variables were measured and digitized at 200, 400 and 800 m from the perimeter of 38 200 m × 100 m strip transects. A mixture of field and landscape variables was associated with the density of savannah sparrow (Passerculus sandwichensis) and grasshopper sparrow (Ammodramus savannarum). Only landscape variables were associated with the density of bobolink (Dolichonyx oryzivorus), eastern meadowlark (Sturnella magna) and all birds that were grassland species of management concern. Field size was not an important predictor of bird density. Cover-type diversity of the surrounding area was commonly selected in the models for three species and all birds that were grassland species of management concern. Higher bird densities in the transects were associated with landscapes where the cover types were less diverse. Landscapes with low cover typ...
TL;DR: Incomplete disturbance of fescue grasslands, by mowing for hay or grazing by cattle, reduced or eliminated Baird's sparrow and Sprague's pipit but permitted the ingress of horned lark and chestnut-collared longspur.
Abstract: The effects of several forms of agricultural use of native fescue (Festuca scabrella) grasslands upon populations of native passerine birds were studied in the Hand Hills of southern Alberta in 1970.Censuses of avian populations were carried out on twelve 40-acre (16.2 ha) study plots as well as on two 10-mi (16.1 km) long roadside routes. The vegetation on the study plots and along the roadside routes was described.Native fescue grasslands, undisturbed for 3 years, supported a passerine community consisting of Baird's sparrow (Ammodramus bairdii), Sprague's pipit (Anthus spragueii), savannah sparrow (Passerculus sandwichensis), clay-colored sparrow (Spizella pallida), and western meadowlark (Sturnella neglecta). Incomplete disturbance of fescue grasslands, by mowing for hay or grazing by cattle, reduced or eliminated Baird's sparrow and Sprague's pipit but permitted the ingress of horned lark (Eremophila alpestris) and chestnut-collared longspur (Calcarius ornatus). Total elimination of the native grassl...
TL;DR: In this paper, the authors measured bird occurrence and corresponding vegetation attributes on mixed-grass prairie in northwestern North Dakota during 1993-1994 and found that ten grassland passerine species occurred commonly (i.e., at >10% of point count locations), including two species endemic to the northern Great Plains [Baird's sparrow (Ammodramus bairdii) and Sprague's pipit (Anthus spragueii)], and several species of management concern [bobolink (Dolichonyx oryzivorus), grassho
Abstract: With grassland bird populations in the Great Plains exhibiting steep declines, grassland managers require information on bird habitat needs to optimally manage lands dedicated to wildlife. During 1993–1994, we measured bird occurrence and corresponding vegetation attributes on mixed-grass prairie in northwestern North Dakota. Three hundred and ten point-count locations over a wide range of successional stages were sampled. Ten grassland passerine species occurred commonly (i.e., at >10% of point count locations), including two species endemic to the northern Great Plains [Baird's sparrow (Ammodramus bairdii) and Sprague's pipit (Anthus spragueii)], and several species of management concern [bobolink (Dolichonyx oryzivorus), grasshopper sparrow (Ammodramus savannarum), clay-colored sparrow (Spizella pallida)]. Some species were ubiquitous and had generalized habitat associations [e.g., savannah sparrow (Passerculus sandwichensis)]. Others exhibited more finely tuned, closely overlapping use of rel...