Trend and periodicity of the wintering population of Ferruginous Duck (Aythya nyroca) in Campania (Southern Italy)

Abstract

The study of trend and periodicity of the Ferruginous Duck wintering population in Campania can provide useful information for the management of a species with a nonoptimal conservation status. At the same time it can indicate a reference value of periodicity for those who want to investigate this aspect, for this species or other birds wintering in the Mediterranean basin, also considering the few number of research carried out on wintering waterbird populations. The TRIM method, used to study the trend, and the Fourier analysis, used to highlight all the harmonics present in the time series, allowed us to establish that the Ferruginous Duck shows in Campania a moderate increase in the winter period and that the wintering populations have a mid-term periodicity equal to a value of 2 years.