Figure. . . . Field sites used for sampling birds in southwest suburban Chicago, Illinois, USA, 2005–2010. Sites consist of residential areas (numbered sites) and urban green spaces (lettered sites). Two residential sites not shown on the map (21 and 22) are ≈20 km north of this region. Box in inset map indicates location of sampling area. Main map shows the landscape gradient of impervious surfaces (National Land Cover Database 2001, US Geological Survey, Sioux Falls, SD, USA): dark gray areas are those with a low proportion of impervious cover (urban green spaces, e.g., forest preserves, parks, cemeteries, riparian buffers); light gray areas and white areas are those with a high proportion of impervious cover (areas with high density of buildings, residential housing, and roads). EC, Evergreen Cemetery; PHN, Palos Hills Natural; PL, Pleasure Lake; WW, Wolfe Wildlife Refuge; HS, Holy Sepulchre Cemetery; SC, Saint Casimir Cemetery.