A massive spoonbill stopover episode: Identifying emergency sites for the conservation of migratory waterbird populations

Abstract

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.