The Aquatic Warbler (Acrocephalus paludicola) is one of the most threatened
migratory passerine birds in the world. The species stops over at both European
and African wetlands during its migration. Using data from a long-term ringing program
in the restored wetland of La Nava (Spain), we describe several aspects of the
species’ stopover ecology at this site with special focus on juveniles: (1) timing of
migration, (2) population size, (3) fuel reposition rate, (4) stopover duration and (5)
site fidelity. We elaborated two Multiple Linear Regressions and a Generalized Linear
Model to estimate the determinants of migration phenology, daily fattening rate and
abundance of captures in addition to minimum observed stopover duration. Finally,
we calculated return rates to estimate stopover site fidelity. We determined that: this
stopover site belongs to an Atlantic migration route; juveniles experience delayed
migration; and that reduced captures are associated with more restrictive hydrological
management. Return rate results suggested that there is stopover site fidelity is low.
Our results may indicate that this stopover site serves primarily as a resting place
rather than a refuelling habitat for this species.