Figure 1
From: Replicated, urban-driven exposure to metallic trace elements in two passerines
Sampling points—(a) Map of Poland highlighting the 8 cities (in black) and 4 protected forests (in green) where blue tits and great tits were sampled. (b) For the 8 cities, we detail human population size, population density and urban area size as defined by administrative borders (data as of 2019 from Central Statistics Poland—GUS).
