Overdijk O.,Working Group Spoonbills International |
Navedo J.G.,University of Extremadura |
Navedo J.G.,University of the Sea
Aquatic Conservation: Marine and Freshwater Ecosystems | Year: 2012
The existence of emergency sites could reduce the mortality rate associated with stochastic adverse weather conditions experienced by migratory waterbirds. However, as they are not regularly used by significant fractions of any population they are not integrated within conservation strategies. A massive stopover of Eurasian spoonbill (Platalea leucorodia) occurred simultaneously at three coastal wetlands in northern Spain (Txingudi, Urdaibai and Santoña) during 3 consecutive days in September 2011. By analysing the resightings of PVC-ringed birds it was estimated that it comprised 18% of the population. At least 23% of these birds made short journeys between sites, the majority (77%) overwintering in Africa. A higher percentage of spoonbills that stopped over at Txingudi overwinter in Africa compared with the other areas. During September 2011 there were more periods of consecutive days with adverse wind conditions than any other year. Furthermore, wind conditions during the massive stopover, as well as precipitation, exerted a continuous negative influence on the resumption of migration, lasting 3 consecutive days. The scarcity of consecutive days with favourable winds and adverse weather conditions further encountered once en route probably led to an emergency strategy developed by a significant fraction of a spoonbill population, with several birds choosing then to make a short diversion in a westerly direction from Txingudi. Since this stopover site usually appears to be skipped during migration, it will not fit Ramsar Criterion 6 for spoonbills even after including the massive stopover (c. 7%), because average numbers will hardly satisfy the requisite of 'regularly supporting' a population. A criterion is proposed to identify emergency sites for the conservation of migratory waterbird populations thus improving landscape connectivity and accounting better for long-term natural variability associated with stochastic adverse events. Being a flagship and umbrella species, the recognition of emergency sites for spoonbills would help the conservation of other associated waterbirds. © 2012 John Wiley & Sons, Ltd.
Navedo J.G.,University of Extremadura |
Navedo J.G.,National Autonomous University of Mexico |
Orizaola G.,Uppsala University |
Masero J.A.,University of Extremadura |
And 2 more authors.
Journal of Ornithology | Year: 2010
Long-distance migration is widespread among birds, connecting breeding and wintering areas through a set of stopover localities where individuals refuel and/or rest. The extent of the stopover is critical in determining the migratory strategy of a bird. Here, we examined the relationship between minimum length of stay of PVC-ringed birds in a major stopover site and the remaining flight distance to the overwintering area in the Eurasian spoonbill (Platalea l. leucorodia) during four consecutive autumn migrations. We also analysed the potential effect of timing (arrival date), as well as the role of experience in explaining stopover duration of spoonbills. Overall, birds wintering in Africa, and facing long-distance travel from the stopover site (ca. 3,000 km) stay for longer (2.7 ± 0.4 days) than Iberian winterers (1.5 ± 0.2 days) that perform a much shorter migration (ca. 800 km). These differences were consistent between years. Stopover duration was not significantly affected by the age of the bird. However, there was a significant reduction as migration advanced. Our results suggest that spoonbills develop different stopover strategies depending on the expected distance to the wintering grounds. Adults, especially long-distance migratory ones, could reduce the potential negative effects of density-dependence processes by avoiding stopover at the end of the migration period. These findings are of significant relevance for understanding differences in migratory behaviour within single populations, especially for declining waterbirds, as well as stress the relevance of preserving stopover localities for the conservation of intraspecific diversity in migratory species. © 2010 Dt. Ornithologen-Gesellschaft e.V.