Impact of military activities on bird species considered to benefit from disturbances: an example from an active military training area in Latvia

We surveyed the military training area Adazi to evaluate the effects of disturbance caused by military activities on the abundance of protected bird species considered to benefit from disturbances at the site (SCBD). We collected data on the abundance of the selected bird species in a set of representative sample plots during three repeated surveys. In each plot we mapped areas affected by different visually detectable disturbances of military origin and areas covered by EU protected habitat types. Overall abundance and richness of SCBD were calculated for each of the surveyed squares. Generalised linear modelling was used to relate the recorded abundance of each species, and the overall abundance and richness of SCBD, with the available habitat and military disturbance parameters. We evaluated a set of competitive models to identify the most important explanatory variables. The modelling results imply clear positive effects of most of the military activities on the analysed species as well as overall species richness. The variables describing the availability of habitats alone could not explain as large variation in the data as together with the disturbance variables, The results show that the recent (up to one year) and moderately recent (up to two years) disturbances were the most important to maintain the habitats. The results suggest that these species tend to occupy the newly created suitable habitat patches in the next breeding season. At the time of the study, there was no measurable negative effect of the military activities on abundance and richness of the analysed species. However, some negative effects of military activities on species behaviour were observed.