Preservation of wild bird species in northern Portugal - Effects of anthropogenic pressures in wild bird populations (2008-2017)

Abstract

In this study we aim to obtain a holistic view over the consequences of human-induced threats to the wild bird populations in the study area, based on data collected from a Wildlife Rehabilitation Centre (WRC) through the method of Partial Least Squares-Path Modelling (PLS-PM). The study area comprised 76 rural and urban municipalities located in northern Portugal. Within PLS-PM the threats ("anthropogenic pressures") are termed exogenous latent variables, while the final environmental consequence (wild bird mortality) is termed endogenous latent variable. Latent variables are concepts assessed by numerical parameters. The PLS-PM results identified as most significant pressures, the number of small and medium companies in the municipalities, both in traumatic and non-traumatic deaths. Although the pattern of weights is similar regardless of the general cause of death, traumatic causes seem to play a more prominent role given the larger weights in the relevant specific causes (number of companies). The high coefficients of determination (R² > 0,8) reveal that the variance of wild bird mortality is largely explained by the variance of the pressures, which indicates a cause-effect relationship between the independent (pressures) and dependent (mortality) variables. The ample coverage of northern Portugal with a huge dataset suggests that this cause-effect relationship is typical from this region. The use of a sophisticated statistical method PLS-PM and its incorporation into a Geographic Information System (GIS) revealed to be an important tool for analysing wildlife impacts of environmental and human factors. The results obtained with this model indicate that there is a substantial negative impact of human activity on wild bird mortality.

Keywords: Anthropogenic pressures; Mortality; North of Portugal; Partial least squares-path modelling; Wild birds.