Methods for Studying Songbird Territories

A brief historical review is presented of the development of approaches to the study of the territorial space of songbirds (Oscines), using both older and current research methods. The study of bird territoriality has continued for more than a century, but there are still not only little-known aspects that remain in this direction, but also no consensus on terminology and methods. The description of the territorial space plays leading roles in such works. In turn, the classic objects of such research are songbirds demonstrating their territories by singing and defending them from invasion by other individuals. There have been many definitions proposed for the term “territory,” which reflect different concepts of territoriality. The most common definition of a territory thereby is a defended (conceptually) and demonstrated (operationally) space. As a rule, this space is a certain area, a projection of the real territory to the surface on the ground. In recent decades, however, publications have appeared on the topic of exploring territories as three-dimensional (3D) structures. The most effective method of field registration of territories remains the territory mapping method based on visual observations of tagged individuals, which has also been adapted for 3D-territories. Alternative approaches to the registration of territories, including radio telemetry, have significant limitations. In terms of quantitative data-processing methods, there has been a shift over the past decades from an analysis of territories as polygons to their analysis as kernel isopleths. This approach allows for not only the territory contours to be understood, but also the frequency of the use of different points within its limits to be assessed. A significant achievement in recent years is the adaptation of the kernel methods to three-dimensional structures. It can be said that there is a need to study the territoriality of birds in the 3D-environment. Such research seems very promising because it can provide fundamentally new information on topics such as habitat selection and space use, the formation of the spatial and ethological structure of settlements, the separation of territories under high population densities and limited resources, and both intra- and interspecific competition.