Management Implications of Cover Selection Data: Northern Bobwhite Example

Abstract: We derived a method of estimating the direction and magnitude of cover changes for potentially maximizing wildlife abundance on an area. We illustrate the method with data on cover selection by northern bobwhites (Colinus virginianus) collected in the Texas Panhandle from 2000 to 2003. We used radiotelemetry to determine use of cover associations, Geographic Information System analysis to determine their availability, and logic related to use-availability analysis to collapse 95% kernel home ranges to usable space. Bobwhites selected mixed-shrub cover consisting of sand plum (Prunus angustifolia) and fragrant sumac (Rhus aromatica), and they avoided or neutrally used 8 other cover associations. However, grass upland and sand sagebrush (Artemisia filifolia) associations occurred in ≥86% of home ranges (n = 96 bobwhites with ≥30 radiolocations). Usable space averaged 54.2% ± 1.72 SE of kernel home ranges. The data indicated that adding about 226 ha of mixed-shrub cover or a structural homologue while simultaneously reducing the quantity of most other cover associations would maximize bobwhite abundance. An area with 30–60% mixed-shrub cover, with the balance in grass upland and sand sagebrush, and with cover dispersed such that no point was >30 m from mixed-shrub cover was hypothetically optimal for bobwhites in our region. Within certain constraints (e.g., financial, social, edaphic), managers can apply this method by manipulating cover types through relevant management practices (e.g., planting, prescribed burning, mechanical removal of vegetation). This method, with minor modification, could also be used to decrease usable space on an area, and thus decrease wildlife densities, should that be the manager's objective.     

Eccentricity in the clypeasteroid echinoid Dendraster: environmental significance and application in Pliocene paleoecology

Stanton, Robert J., Jr., Dodd, J. Robert & Alexander, Richard R. 1979 01 15: Eccentricity in the clypeasteroid echinoid Dendraster: environmental significance and application in Pliocene paleoecology. Lethaia . Vol. 12, pp. 75–87. Oslo. ISSN 0024–1164.
The echinoid Dendraster lives in the northwest Pacific in environments ranging from open exposed coast to protected embayment. Water energy and the abundance and quality of food along this environmental gradient are correlated with test size and eccentricity of the apical area, so that larger and more eccentric specimens occur on the open coast than in bays. Study of Dendraster in Pliocene strata of the Coalinga California region indicates that these morphologic characteristics provide valuable information for paleoenvironmental reconstruction. Lateral and temporal environmental gradients within a broad Pliocene embayment and the location and size of the bay entrance can be determined on the basis of Dendraster eccentricity and size. Several species and subspecies of Dendraster in the Pliocene of the Coalinga region, described largely by differences in eccentricity, are probably not valid taxa but are merely ecophenotypic expressions of the laterally and temporally variable environment.