Census of swift colonies in medium-large cities: seven cases from N-Italy

Given worldwide rapid human population growth, resulting in loss of natural habitats and increase of urban areas, it is important to understand how anthropogenic factors affect species presence, and consequently how well species tolerate or adapt to human altered environments. Several swift species utilize cavities in buildings, towers, churches and other anthropic constructions as nesting sites. However, swifts are facing pressures related to the recent tendency to close all the holes to hamper their use by pigeons or to reduce thermic dispersions of buildings. To achieve a good management and conservation of urban populations of swift, detailed maps of building positions and the holes utilized is required. In 2018-2019 we compared the census methods and the effort required to map swift colonies (Common, Pallid and Alpine swifts) in medium-large cities of NW-Italy. Five medium size cities (Asti, Bergamo, Biella, Novara, Vercelli: 40-120.000 inhabitants) were inspected by small teams (1-3 (8) persons), with walking transects in the historical centre. Each transect was repeated three times during the breeding season. Buildings identified were then mapped drawing on pictures the cavities utilized by swifts (at least three 2-hours sampling in different days). The method allowed the precise localization of an average 31 constructions utilized by swifts (range 17-59). Two large cities (Bologna, Milano: 400-1.400.000 inhabitants) were inspected in a selected portion of the historical centre. In Milano 3 professionals and 10 volunteers of a citizen project were employed, and 60 colonies were localized in a 17 km² area. In Bologna, inspections (1 person) were spent to map hole positions on 5 historical building. The working examples here reported for N-Italy show the feasibility of censusing medium-size cities (and part of large cities as well) by small research teams or citizen science projects. The data collected will be essential to hamper future negative management of swift nesting sites.