Competition is a major limiting factor of refueling in migratory passerines during stopover

For an avian migrant, refueling capacity attainable during stopovers governs the entire migration schedule and, ultimately, its fitness. Specifically, timely replenishing energy stores is critical when migration involves crossing ecological barriers, within which refueling may be limited. Here, we tested the hypothesis that fuel deposition rates (FDRs) of migratory passerines within barrier-edge stopover sites are constrained by the density of potential competitors, irrespective of migration season, phenology, and local environmental conditions. We also evaluated diverse intra- and inter-specific competition scenarios and explored a potential mediation of density-dependence by environmental factors. The analyzed data, collected by us over 13 consecutive years (2009–2022), contains information on seven species of long-distance migratory insectivorous passerines measured within eight desert-edge habitats throughout autumn and spring migrations. As predicted, our analyses revealed negative..., ,