Monday 4 April 2011


Flock of Greylag Geese (Anser anser). Casas de Hitos lake, Navalvillar de Pela, Badajoz. 22-01-2011. Juan Pablo Prieto.

The traditional wintering areas for Greylag Geese (Anser anser) in Spain are in the northern plains of Spain, the "meseta norte" (Zamora and Palencia) and in the saltmarshes of the River Guadalquivir in the south. Until a few years ago these two areas accounted for almost the whole Iberian population. Extremadura lies between these two spots and all geese heading for Doñana must overfly it. For decades they did just that, flew straight over without hardly stopping. This stands to reason given the dearth of natural wetlands in Extremadura. The figures are telling: the January counts from 1978 to 1989 throw up the paltry mean figure of 59 Greylags wintering in the area. But two factors brought about a change in this situation; firstly the construction of more reservoirs and irrigated farming land and secondly the increase in the European Greylag population. From 1991 to 1995 the mean number of wintering Greylags in Extremadura soared to 2700, increasing almost fifty-fold, with peaks of 3750. The standout site is Valdecañas Reservoir in northeast Cáceres, with 33-65% of the total. The rest are spread around large and medium-sized reservoirs, each of which holds at most a few hundred birds. During the next seven winters no January counts were made in Extremadura but the general impression was of a continuing upward trend. At the turn of the century the number of wintering Greylags perhaps topped 5000 for the first time. The January count of 2002 came out as 4500 in the province of Cáceres alone and an estimate of 8000 for the whole of Extremadura. The renewed regional counts as from January 2003 bear this out, with figures that were undreamt of only a few years back. The 2006 count was 19,043 Greylags and 10,380 in 2007. Numbers seem to have been quite similar in 2010 and 2011. Nonetheless, a detailed look at the figures shows that in most places, mainly reservoirs, the numbers have held pretty steady since the 1990s. Barring one district: the Vegas Altas of Guadiana, where the massive takeup of irrigated farming created the conditions for a new and sizeable wintering area for Greylags. This district now boasts 14,000 birds, sometimes up to 90% of Extremadura's wintering Greylags, most of them feeding in maize and rice stubble. This poses a stiff and thrilling challenge for birdwatchers for these huge flocks often have a few stowaways of the rarer and much sought-after geese species.

Greylag (Anser anser) in Extremadura. The red bars show the figures recorded in the official January counts (DGMN, GIC-UEX, SEO/BirdLife). The blue bars show estimates for years without a count or not yet published (2010). Some official counts (e.g.2008) are partial, given that the main aim was to count the wildfowl in wetlands and many of Extremadura's wintering Greylags live and feed in cropland that does not come into the wildfowl count. Another factor that hinders counts is that geese do not usually form winter roosts in Extremadura.