Status, Distribution and Long-Term Changes in the Waterbird Community Wintering in Don˜ Ana, South–West Spain

www.vetalapalma.es 1 Bird ecology in Doñana area: status, distribution and population trends. Ecología de las aves en el área de Doñana: status, distribución y tendencias poblacionales. BIOLOGICALCONSERVATION 141 (2008) 1371 – 1 3 8 8 available at www.sciencedirect.com journal homepage: www.else vier.com/locate/biocon Status, distribution and long-term changes in the waterbird community wintering in Don˜ ana, south–west Spain M.A. Rendońa,1, A.J. Greena,*,1, E. Aguilerab, P. Almaraza aDepartment of Wetland Ecology, Estacioń Biolo´gica de Don˜ ana-CSIC, Avda. Marıá Luisa s/n, Pabelloń del Peru´ , Sevilla 41013, Spain bDepartment of Behavioural Ecology, Estacioń Biolo´gica de Don˜ ana-CSIC, Avda. Marıá Luisa s/n, Pabelloń del Peru´ , Sevilla 41013, Spain ARTICLEINFO ABSTRACT Article history: The Guadalquivir Marshes or Don˜ ana wetland complex is the most important wintering Received 21 November 2007 site for migratory waterbirds in the Mediterranean region. However, there is a lack of pre- Received in revised form vious information on the status of different species in this area. Using monthly aerial 5 February 2008 counts conducted from 1978 to 2005, we analysed the size of wintering populations of 21 Accepted 8 March 2008 waterbird species, their distribution within the Guadalquivir Marshes, and their long-term Available online 29 April 2008 population trends. We used Underhill indices to replace missing values and to correct for flocks of unidentified ducks. Based on long-term means, we identified 16 species whose Keywords: populations at Don˜ ana exceed 1% of the biogeographical flyway population. For at least 1 Wetlands month of the year, mean counts were around 10% of the flyway population for six species. Aerial counts The natural, temporary marshes of Don˜ ana National Park were particularly important for Population trends Anatidae, ricefields for gulls, white storks and grey herons, fish ponds for flamingos, cor- Habitat transformation morants and avocets, and salt pans for shelduck. Four Anatidae species have undergone Migratory status long-term declines and eight non-Anatidae have undergone long-term increases. Popula- Trophic guild tion trends were related with trophic guild, migratory status and habitat use. Winter visi- tors and herbivorous species showed more negative trends than resident, omnivorous– carnivorous species. Those species concentrated in strictly-protected natural marshes have tended to decline. The surface area of ricefields and fish ponds has increased over the study period, and bird species concentrated in these artificial wetlands have tended to increase. This raises questions about the value of waterbirds as flagship or umbrella species for wetland conservation. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction fields has increased in many areas, and these provide alterna- tive habitats for waterbirds (Elphick and Oring, 1998; Elphick, Human activities have caused loss and degradation of wet- 2000; Tourenq et al., 2001b; Ma et al., 2004). However, the net lands worldwide (Moser et al., 1996). In Europe more than consequences of such habitat transformation for waterbird 50% of natural wetlands have been lost, mainly due to drain- populations remains unclear (Day and Colwell, 1998; Elphick, age for agricultural use, and all remaining wetlands are af- 2000; Ma et al., 2004). For example, there is little information fected to some extent by human activities. In contrast, the as to which waterbird species are better able to adapt to such surface area of artificial wetlands such as fish ponds or rice- transformed habitats, and which are more dependent on * Corresponding author: Tel.: +34 95 4232340x241; fax: +34 95 4621125. E-mail address: [email protected] (A.J. Green). 1 These authors contributed equally to this work. 0006-3207/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.biocon.2008.03.006 www.vetalapalma.es 2 Bird ecology in Doñana area: status, distribution and population trends. Ecología de las aves en el área de Doñana: status, distribución y tendencias poblacionales. 1372 BIOLOGICALCONSERVATION 141 (2008) 1371 – 1 3 8 8 wetlands in a natural state. In particular, few studies have tify those species present in internationally important num- been able to compare bird counts in the same area before bers (i.e. more than 1% of the total flyway population, and after habitat transformation has occurred. Wetlands International, 2006); (2) to identify long-term trends The wetlands within the delta of the River Guadalquivir in and seasonal patterns (i.e. phenology within a winter) for south–west Spain (also known as the marismas del Guadal- each bird species; (3) to quantify the distribution of each spe- quivir, the Guadalquivir marshes or Don˜ ana wetlands) have cies between the different major natural and transformed long been recognised as one of the most important habitats habitats found in GM; (4) to assess the relationship between for waterbirds in the Western Palaearctic (Chapman and long-term trends for different species and their habitat use, Buck, 1910), and a steadily increasing proportion of remaining trophic guilds and migratory status; and (5) to consider the wetlands have been protected since the 1960s (Garcıá-Novo conservation implications of our findings. and Marıń, 2006; Fernańdez-Delgado, 2006). However, despite some studies of the ecology of wintering waterbirds (e.g. 2. Materials and methods Amat, 1981, 1986), there is a shortage of detailed studies on the numbers and distribution of waterbirds wintering in the 2.1. Study area Guadalquivir marshes (GM from hereon). Based on analyses of midwinter counts carried out during the International GM is a mosaic of extensive wetlands of deltaic origin located Waterbird Census (IWC), GM is known to be the most impor- in south-Western Spain (37°N, 6°250W) (Fig. 1A). The marshes tant site in the West Mediterranean for many wildfowl (Anati- occupied c. 180,000 ha in 1900, but drainage for agriculture dae) species (Scott and Rose, 1996). GM is also the most and other transformations have gradually reduced the important wintering site in the Iberian Peninsula for many remaining area of natural marshes to c.30,000 ha, almost all other waterbirds (Martı´ and del Moral, 2002). of which is protected within the Don˜ ana National Park (Engg- Here, we present the first detailed analysis of the numbers ass, 1968; Garcıá-Novo and Marıń, 2006). The climate of GM is of waterbirds wintering in GM, and of their distribution be- Mediterranean sub-humid with rainy winters and dry sum- tween major habitat types therein. The area is too large and mers. During the study period the mean winter precipitation inaccessible to count effectively from the ground. We take (September–February) was 422.6 mm (coefficient of variation, advantage of an extensive data set of aerial counts from CV = 47%), accounting for more than the 70% of annual rain- 1977 to 2005, which has not previously been subject to de- fall (data collected at the Palacio de Don˜ ana). tailed analysis. Our main objectives are as follows: (1) to The total area covered during the aerial surveys is quantify the size of wintering populations in GM, and to iden- 91,890 ha, divided into four main sectors (Fig. 1A): A B 900 800 700 600 500 400 300 Precipitation (mm) 200 100 0 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 C 45000 40000 35000 30000 25000 20000 15000 10000 Flooded rice field (ha) 5000 0 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Fig. 1 – (A) Location of the study area and satellite image of the Guadalquivir marshes, showing the four main areas included in the aerial counts (PNC: Parque Nacional, PNT: Parque Natural Norte, SB: Salinas de Bonanza, VLP: Veta la Palma). (B) Accumulated precipitation (September–February) at the Palacio de Don˜ ana from 1978 to 2005. (C) Area of ricefields cultivated in the Guadalquivir marshes from 1978 to 2003. www.vetalapalma.es 3 Bird ecology in Doñana area: status, distribution and population trends. Ecología de las aves en el área de Doñana: status, distribución y tendencias poblacionales. BIOLOGICALCONSERVATION 141 (2008) 1371 – 1 3 8 8 1373 (1) Parque Nacional (PNC) represents the natural, seasonal 2.2. Survey methods marsh within Don˜ ana National Park (29,640 ha). The seasonal marsh floods when heavy rains arrive between October The populations of waterbirds on the GM have been estimated and March and is generally completely dry between July and by monthly aerial survey since 1977 as part of a monitoring October (Montes et al., 1998; Garcıá-Novo and Marıń, 2006). program carried out by the Don˜ ana Biological Station (http:// The peak area inundated varies greatly between winters www-rbd.ebd.csic.es/Seguimiento/seguimiento.htm). We fo- according to precipitation (Fig. 1B). Satellite data indicate a cussed on the wintering period from November to February, mean winter flooded area (January) of 12,881 ha (CV = 70%) and refer from hereon to a given winter by the year in which for our study period (J. Bustamante et al., unpublished data). it ends (e.g. winter 1978 is November 1977 to February 1978). PNC is now heavily protected and declared a Biosphere Re- However, we summarise data from other months to establish serve (in 1980), Ramsar site (in 1982) and UNESCO World Her- the phenology of each species in the study area (Appendix B). itage Site (in 1994). Although the entire PNC sector has been Aerial surveys lasted 1.5–3 h in the morning, depending on included within the National Park since 1978, hunting of the extent of the study area inundated at that time.

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