The Black-Tailed Godwit (
Limosa limosa) is an exceptional breeder in Extremadura (only one known case), a rare winter visitor, common on spring passage (30,000 birds) and rare on post-breeding migration. The region is recording an upward trend of birds on passage even though Europe as a whole has recorded a “moderate decline” with a 40% drop in the eight-year period running from 1999 to 2006 (PECBMS, 2009). It is listed as Near Threatened in the 2010 IUCN Red List Category
.
The post-breeding congregations in the stubble-free flooded ricefields of Vegas del Guadiana is a fairly recent phenomenon. In the mid 1980s the species made no stopovers in Extremadura; numbers had built up to about 4000 by 1990 and it was not until the start of the C21st that numbers settled down at over 25,000 birds. In recent years the flock sizes within the Vegas Altas area have dropped in the east (Palazuelo-Madrigalejo) and increased in the west (Santa Amalia, Hernán Cortés and Yelbes), where they have been most abundant in the 2004-2007 period. There are other minor, more sporadic flocking areas in Vegas Bajas, La Albuera, Llanos de Cáceres and Vegas del Alagón (Masero et al., 2008).
The population in the
Vegas del Guadiana has been closely studied in the 2004-2007 period by the Conservation Research Group of Extremadura University (GIC-UEX in Spanish initials), colour ringing 341 birds. From plumage details 8% of them were identified as
L.l. islandica, a race that mixes with the dominant
L.l. limosa and is observed in the same spots and on the same dates. Ringed birds seen in Extremadura came from Holland (86%,
limosa race), Iceland and UK (10% and 4% respectively,
islandica race). Birds ringed in Extremadura, for their part, have been spotted in Iceland (3%,
islandica race), Holland (70%), France (13%), Germany (6%), Belgium (6%) and Denmark (2%); 97%, therefore, in zones of the
limosa race. The return rate (ringed birds returning in latter seasons) is estimated to be 36%, with movements about the Iberian peninsula being noted: 6% of Extremadura-ringed birds are seen in Portugal, even in the same season, and 31% of Cádiz-ringed birds are seen in Extremadura in the same year or following years (Masero
et al., 2009).
To find out the length of stay 24 birds were caught and radiomarked in 2004. Two waves of incoming migration were detected, the first around 20 January (17 January in 2004) and the second around 10 February (7 February in 2004). The birds of the first incoming wave were still in winter plumage and hardly moulted at all into summer plumage during their Extremadura stay, even though the stay was longer (minimum estimate of 40 days) and their departure later (1 March on average). Over sixty percent of the birds of the second wave arrived in summer plumage, staying for a shorter time (minimum stay of 17 days) and left one week earlier (24 February on average). The average stay for the whole set of birds under study was 22 days, all of them having left by 15 March. The stopover time on spring passage is deemed to be a key factor in the success rate of the following breeding season.
The simultaneous counts carried out in the
Vegas del Guadiana, displayed on a graph, peak steeply, then falling away gently before a sharp drop in February (varying between the first and last week of the month in different years). The average maximum count is 24,200 with an all-time high of 27,643 on 07/02/04; this represents at least 15% of the migratory population on the East Atlantic route. A comparison with other spots on the Iberian Peninsula shows that
Doñana records highs of up to 48,000 birds, usually peaking earlier than in Extremadura (December in 2002-2006; January in 1999-2001), while the Portuguese estuaries of the Tagus and Sado rivers show a similar pattern to Extremadura, with February highs (e.g. 44,700 birds in February 2006). Other important Iberian stopover points are
Bahía de Cádiz and
Marismas del Odiel in Spain and
Ría Formosa, Castro Marim and Ría de Aveiro in Portugal. Recent decades have recorded a big increase in the number of Black-Tailed Godwits in Extremadura and Doñana, offsetting the declining numbers in traditional stopover points in Northwest Africa. Taken as a whole, Southwest Iberia plays a functional role in the spring migration of Black-Tailed Godwits (Masero
et al., 2010), merging into the end of the wintering phase.
References:
Masero, J. A., Santiago-Quesada, F., y Sánchez, J. M. 2008. Aguja colinegra Limosa limosa. In: Catálogo regional de especies amenazadas de Extremadura. Fauna II. Clase Aves, 194-195. Consejería de Industria, Energía y Medio Ambiente. Junta de Extremadura. Mérida.
Masero, J. A., Santiago-Quesada, F., Sánchez-Guzmán, J. M., Abad, J. M. and Albano, N. 2009. Geographical origin, return rates, and movements of the near threatened black-tailed Godwits Limosa limosa staying at a major stopover site of Iberia. Ardeola 56: 253–258.
Masero, J. A., Santiago-Quesada, F., Sánchez-Guzmán, J. M., Villegas, A., Abad, J. M., Lopez, N., Encarnaçao, V., Corbacho, C. y Morán, R. 2010. Long lengths of stay, large numbers, and trends of the Black-tailed Godwit Limosa limosa in rice fields during spring migration. Bird Conservation International (on line 27-january-2010).
PECBMS. 2009. The State of Europe’s Common Birds 2008. CSO/RSPB. Prague. Czech Republic.
Pato colorado (Netta rufina). Macho nupcial. Por Javier Prieta.
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On the other hand we are saddened to see Extremadura bucking this bright trend, with a 16% downturn, 8 pairs fewer, in only two years. No other region has seen a reduction in any year of the last decade; Extremadura has now plunged from the region with most Imperial Eagles to last place.
It would now be enlightening if the authority responsible for the conservation of this species gave more information to bear out or rebut these figures. This is unlikely to happen, however, since little or no information is given on the monitoring of threatened species, despite the general interest. Little or nothing was said about the sudden increase from 40 to 49 pairs in two years and we have no idea how it came about. Now we know just as little about this decline or its causes. At least census figures are forthcoming for Monfragüe, showing that the population has held steady at 12 pairs in recent years.
