Site selection and nest success of ring-necked pheasants as a function of location in Iowa landscapes

Wildlife managers in the midwestern United States implicitly recognize that large-scale changes in land use have been a major factor in the nesting ec ology of the ring-necked pheasant (Phasianus colchicus), but they have lack ed models that quantify the relation between nest success and landscape var iables at multiple scales. We used data from 288 nests of radiomarked femal e pheasants during the 1990-94 breeding seasons in Iowa to study nest-site selection and nest success. We quantified habitat and landscape metrics wit hin the 485-m radius of a home range around nests by using aerial imagery a nd FRAGSTATS. We screened potential landscape variables by using principal component and classification and regression tree (CART) analyses before dev eloping logistic regression models to predict nest-site selection and succe ss as a function of landscape conditions. A 5-variable logistic regression model incorporating nesting patch size, mean grassland patch size, landscap e core area, landscape shape index, and distance to edge predicted nest-sit e locations at a 77% posterior concordant rate. The CART analyses suggested nest success was best modeled by splitting nest observations into nests in patches less than or equal to 15.6 ha and >15.6 ha. For nests in patches l ess than or equal to 15.6 ha, a logistic regression model with site cover t ype and mean core area index predicted nest success with a 73% posterior co ncordant rate (P < 0.001). For nests in patches >15.6 ha, a model with site cover type, core area standard deviation, and distance from the nest to th e edge predicted nest success best (concordant rate = 64%, P = 0.069), alth ough the effect of distance of edge was very slight (conditional odds ratio = 1.003, 95% CI = 0.997-1.009). Our models suggest managers should strive to provide undisturbed grassland blocks greater than or equal to 15 ha for nesting pheasants, but our observation was the success was highest in field s 4 times that size. Furthermore, cover in several large grassland blocks w ithin the nesting home range is preferable to concentrating cover in 1 larg e block. Landscape models like ours could be used to project the consequenc es of changes in agricultural policy on ring-necked pheasant populations.