No abstract

A large literature exists on population dynamics of ring‐necked pheasant (Phasianus colchicus) in North America, but there has not been an attempt to formulate a matrix model nor a sensitivity analysis of the relationships between vital rates and population finite growth rate (Λ) that can be used to guide management. We summarized demographic data available from a 5‐year field study in Iowa, USA, collected in Kossuth County (low composition of perennial habitat) and Palo Alto County (high composition of perennial habitat) into a 2‐stage (young and adult) matrix projection model. We estimated Λ1 (the dominant eigenvalue of the deterministic matrix), the stable age distribution (ω), relative reproductive value vector (n̈), other demographic parameters, and Λiid, a bootstrap estimate of growth that includes interannual variation in life history parameters. We analyzed the relative importance of vital rates on population growth rate using sensitivity and elasticity of both matrix elements and lower‐level parameters such as winter survival and nest success. We first characterized general life history using averaged data from both areas and all years that yielded Λ1 = 1.086, and a stable stage distribution of. Minimum success of the initial nesting attempt (H1) that would maintain Λ ≥ 1 under average conditions was estimated to be 42%. Changes in Λ1 were most sensitive to survival of chicks during brood rearing (SB), followed in importance by survival during the subsequent winter (SW), followed by H1. We followed the general analyses with analyses that helped us to focus on the differences in the landscapes of northwest Iowa. Λiid was ≥1 in only 9% of simulations of data from Kossuth whereas estimated Λiid was ≥1 in 88% of simulations from Palo Alto. Our analyses of the relative importance and interactions between SB, SW, and total recruitment (M, including H1 and renesting), if combined with data more specific to a local area, would guide management aimed at affecting multiple life history stages whose relative importance will vary across the landscape.

Range‐wide declines in northern bobwhite populations (Colinus virginianus) have been attributed to concomitant loss of breeding habitat. Bobwhite management efforts to restore this habitat resource can be informed by empirical studies of associations between breeding success and multi‐scale habitat attributes. We compared bobwhite nest success in 2 southern Iowa landscapes as a function of microhabitat and landscape composition. Lake Sugema Fish and Wildlife Area (LSWA) was managed to promote bobwhite recruitment, and Harrisburg Township (HT) was an adjacent landscape dominated by private agricultural production. Survival rate modeling based on telemetry data provided evidence for age‐specific daily nest survival rate. Daily survival rates decreased as nest age increased, but the decline was more severe at HT. Nest survival at LSWA (S = 0.495, SE = 0.103) was nearly twice that on HT (S = 0.277, SE = 0.072). We found no evidence that habitat composition or spatial attributes within 210 m of a nest site significantly influenced nest success. Forb canopy at the nest site had a positive influence on nest success at HT but not at LSWA. We suggest nesting habitat with greater forb canopy cover will increase the opportunity for nesting success in landscapes with limited nesting habitat. © 2010 The Wildlife Society.

An increasing number of state and national databases are available to assess agricultural and environmental trends in natural resource populations. We use a case study approach to consider methodologies for combining state and national data to assess the impact of agricultural policy on state wildlife populations. The scientific question is to assess the impact of the Conservation Reserve Program on pheasant populations in Iowa, using land cover/use data from the National Resources Inventory and count data from an annual state pheasant population survey. Our approach involves identifying a common spatial polygon for linking summaries from each of two datasets, and then estimating parameters that describe temporal trends in land cover and in pheasant populations over a common time period within each polygon. Estimated pheasant population parameters are regressed on land cover summaries to investigate the impact of the Conservation Reserve Program on pheasant populations in regions of the state. Results reveal that the population response to the Conservation Reserve Program varies by region in relation to the physiography and agricultural use of the region, in ways that were not anticipated by policy developers. Statistical considerations for developing appropriate models for combining data are discussed.