International importance of Extremadura, Spain, for overwintering migratory dabbling ducks: a role for reservoirs

• Published in: Bird conservation international 2012-09, Vol.22 (3), p.316-327
• Main Authors: NAVEDO, JUAN G., MASERO, JOSÉ A., SÁNCHEZ-GUZMÁN, JUAN M., ABAD-GÓMEZ, JOSÉ M., GUTIÉRREZ, JORGE S., SANSÓN, ESTHER G., VILLEGAS, AUXILIADORA, COSTILLO, EMILIO, CORBACHO, CASIMIRO, MORÁN, RICARDO
• Format: Article
• Language: English
• Subjects: Anas acuta; Aquatic birds; Artificial wetlands; Habitat improvement; Migratory birds; Overwintering; Penelope; Reservoirs; Rice fields; Strepera; Waterbird Ecology
• ISSN: 0959-2709; 1474-0001
• DOI: 10.1017/S0959270911000311

Many migratory waterbird populations are in decline and loss of natural wetlands is one of the main causes. However, some species may respond positively to artificial wetland recreation. In Extremadura (south-west Europe), several large reservoirs were created for irrigation since the 1960s and some comparatively small reservoirs were built from the late 1990s onwards close to rice fields. Here we analyse the abundance of wintering dabbling ducks (Anas spp.) in Extremadura before (1991–1994) and after (2007–2010) the creation of these new reservoirs in order to address the current importance of the area for this guild within the East Atlantic Flyway (EAF). A mean of 25,277 dabbling ducks wintered in the study area during 1991–1994, increasing to 46,163 individuals during 2007–2010. After controlling for environmental variables, Northern Pintail Anas acuta, Common Teal A. crecca and Northern Shoveler A. clypeata experienced significant increases in the area between both periods, and only Eurasian Wigeon A. penelope suffered a significant decrease. Mallard A. platyrhynchos and Gadwall A. strepera populations did not show any significant trend. The large older reservoirs experienced overall population decreases between the two periods, with four new reservoirs holding more than 35,000 wintering dabbling ducks. Our results reflect an overall improvement in habitat conditions, driven by the creation of reservoirs near to rice fields that could have resulted in a partial redistribution of wintering dabbling ducks in the EAF. The area emerges as one of the most important wintering sites for dabbling ducks in southern Europe, regularly exceeding two of the Ramsar Convention criteria for the conservation of several populations. The protection of these new reservoirs by legal mechanisms would guarantee the existence of a large functional wetland area, which could also mitigate the loss of natural wetlands for populations using the EAF.