Life history parameters
A birds’ lifestyle and environment likely affect needs for feathers, and so we attempted to quantify many life history and environmental parameters for each species. All calculations of life history and environmental parameters were conducted in R version 3.3.1 (R Core team 2016). Spatial data were extracted using shapefiles of species distributions provided by Birdlife International and NatureServ (Birdlife International 2016). We worked with the shapefiles of spatial distributions of Parulidae using the packages GISTools (Brunsdon and Chen 2014), maptools (Bivand and Lewis-Koh 2016), raster (Hijmans 2016), and geosphere (Hijmans et al. 2005) in R. We chose to quantify life history and environmental parameters that reflect factors that may result in feather wear from solar exposure due to distribution and migratory behavior, as well habitat use and foraging stratum. These parameters are migratory distance, breeding latitude, wintering latitude, day length experienced throughout the year, breeding and winter habitat, breeding and winter foraging stratum, nest type, intensity of solar radiation experienced over the year, intensity of solar radiation experienced in the breeding and wintering range (separately), and precipitation, minimum maximum and mean temperature, and elevation, on the breeding and wintering ranges, separately. We also calculated body mass. Below, we detail how we measured or scored these parameters.