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Ornithological Science
Abstract
Abstract
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.
Ringing was carried out by volunteers from the “Estación Biológica de La Nava” (Global Nature Foundation) ringing group, with funds from the LIFE project “Conservation of the Aquatic Warbler in the ZEPA La Nava-Campos” (LIFE02 NAT/E/8616). The expert advice of Paola Laiolo (University of Oviedo) and Giacomo Tavecchia (IMEDEA) was essential to achieving the aims of this study. Hydrological information was provided by Pablo Zuazua and Enrique Gómez (Junta de Castilla y León). The very helpful comments by Javier Seoane (Autonomous University of Madrid) and María José Fernández (University of Valladolid) improved the statistical and meteorological aspects of the study, respectively. A special acknowledgment is dedicated to the ringers Carlos Gutiérrez-Expósito, Manuel Sánchez-Rodríguez, Mariano Torres and Carlos González for their participation in fieldwork.
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