Bird Species . Flight Distance Standards . The distances birds typically fly between stopovers vary widely across species and also depend on the availability of food and cover, as well as on local weather conditions. In the Flyway Model we employ the concept of a distance standard, which determines whether or not one county is reachable from another county in a single flight. Distance standards are used to determine the extent to which the stopover network is connected and the extent to which it provides coverage for flyway region.
Wetlands provide a major source of habitat for many migratory birds during their migration cycles.
NWI data were gathered for the 715 counties used in this study. The prevalence of wetlands in a county was used as a surrogate for the habitat suitability of the county, with more wetlands implying greater suitability. Land Costs . In addition to characterizing counties by the presence of wetlands, we also sought to characterize counties by land costs. From an economic perspective, counties with lower land costs would be more desirable as stopover locales than counties with higher land costs.