Modeling the Dynamics of Avian Populations in Europe (1980–2019) through Generalized Additive Mixed Models

The population abundance of birds is an important way to gauge the sustainability and health of the environment. However, several factors influence their distribution and density in different habitats. This paper aims to provide a comprehensive and updated outlook on bird population dynamics in Europe in the past 40 years. With the use of Generalized Additive Mixed Models (GAMMs), we analyzed the data available from the Pan-European Common Bird Monitoring Scheme (PECBMS) on abundance indexes collected throughout Europe from 1980 to 2019 and explored the driving forces behind our observed changes for each habitat type. We also apply GAMMs to model the overall changes in abundance indices of eight bird species that showed the highest variations (i.e., Locustella fluviatilis, Locustella naevia, Alcedo atthis, Bombycilla garrulus, Tetrax tetrax, Tringa totanus, Anthus campestris and Larus ridibundus ). It was noted that the general abundance of birds decreased, with farmland birds suffering the biggest decline. Forest bird species population abundance was found to be quite varied; specialist species decreased as compared to generalists, which generally increased.