Steady turnover in a bird community in a periurban landscape in Northern Italy: a look at the change in species richness over time

From November 2017 until February 2022, with a partial interruption during 2020 linked to the COVID 19 pandemic, the bird community was monitored in a 30 hectares periurban plot in north-western Lombardy, in the province of Varese. The study area consists of a mosaic of farmland/ urban habitat (Luino and Germignaga municipalities) with scattered strips of woodland on the east side of Lake Maggiore. The farmland is mainly cultivated ryegrass or maize and permanent grassland. The turnover and phenology of the avifauna was regularly monitored. The year was divided up 4 seasons: winter, spring migration, breeding season and autumn migration. Each season was further divided into 10-day periods, giving a total of 37 ten-day periods over the whole year. For each ten-day period, there was a minimum of 4 surveys, alternating a 500m transect over 30 minutes with a single point count for 30 minutes. A total of 134 species were observed. The trend in species richness follows a sinusoidal curve relating to the migration periods. The area of farmland, while not having any regularly breeding species, supported 65 foraging species, with permanent grassland being more species rich than either maize or ryegrass. The Sorensen Similarity Index, based on incidence matrices, ranged from the lowest value of 0.6480 (during the winter of 2018/19 to spring migration in 2019) to the highest value of 0.8572 (from spring migration 2019 to the breeding period in 2019). Most of the nesting species are synanthropic, occupying the urban areas of this plot, including a colony of northern house martins.