Recovery of a wader bird of conservation concern (pied avocet, Recurvirostra avosetta) after wetland restoration: A 17-years study

Abstract

Waders (Charadriiformes) are birds sensitive to change in water levels in wetlands. In this paper, we report a multi-year trend in abundance of adults, nesting pairs and chicks of a biogeographically isolated population of pied avocet (Recurvirostra avosetta L., Aves, Charadriiformes) localized in a salt-water wetland of central Italy where restoration interventions were carried out in 2009. Our hypothesis is that the actions aimed to regulate water levels have allowed the establishment of a stable local population of this rare species. We used a standardized transect methods to obtain values of abundance during the breeding periods (April-July) along the 2006–2022 time range. Comparing data before and after the interventions, we observed an increasing trend in the abundance following the water regulation interventions leading to the establishment of a stable population. The difference in abundance between before and after the restoration was also evident by controlling for rainfalls. When comparing the effects of wetland restoration with rainfall data, we observed as the former was the main predictor (multiple regression) in determining the abundance of pied avocets. The logistic GLM analysis indicates a threshold of 20 individuals comparing before and after the restoration suggesting as the interventions exceed the threshold for the establishment of a stable population. Pied avocet may be an indicator of restoration effort in salt wetlands, since this wader meets many of the typical criteria requested for a biological indicator.