Individual variation in niche use between seasons in migratory birds

Each year, billions of migratory birds cross the globe, occupy various locations throughout the annual cycle and contribute to ecosystem functions globally. Despite their widespread presence, detailed information on occupied habitats and roles in food webs throughout the entire annual cycle is often lacking. Using stable isotopes, we reconstructed the niche positions of 258 individuals from 10 migratory passerine species. Our aim was to examine three hypotheses explaining individual variations in niche positions between seasons. We revealed substantial variability among individuals in niche differences across seasons for all studied species, exhibiting diverse foraging strategies, diets, and non-breeding regions. This variation aligns with the predicted Scenario 3. Our results indicate that migratory species possess a considerable capacity for mitigating the adverse effects of environmental changes via individual variation in niche use.

This contribution includes the dataset and R code.