A large number of studies show that variation exists within variables such as diet items or prey size (Eltonian variables), and that intraspecific variation can influence the outcomes of demographic rates, competition, and predator-prey interactions. Although intraspecific variation among Eltonian niches is established, it cannot be concluded that this variation is reflected in Grinnellian niches—such as temperature or precipitation—because resources such as prey items and size can vary within the same environmental conditions. Investigation of intraspecific variation in Grinnellian niches is now possible due to advances in animal tracking technology and availability of fine-grained, remotely sensed time-series environmental variables. Here, using a dataset of white stork (Ciconia ciconia) movement tracks from 23 populations (440 individuals), we construct and compare individual Grinnellian niches by describing fine-grained environmental associations of individuals.
We show that within each population and for randomly selected pairs among populations, no storks have equivalent individual niches if not accounting for available area (equivalency tests). Furthermore, most storks do not have equivalent niches after accounting for available area (similarity tests). These results imply that individual variation in environmental associations may play an important role in the structure and dynamics of species’ geographic ranges.