Aeroecological observation methods

Observation of animals flying in the atmosphere is the core empirical process of aeroecology. For species that are small, or that fly by night or at high altitudes, this presents a considerable challenge. Even for the more visible species and for flights near the ground, recording the animals' movements requires specialised techniques. Fortunately, continuing rapid advances in radio and optical technologies, electronics, and computing are providing numerous opportunities for developing new and improved observing capabilities. The larger, more complete, and more precise observational datasets that these new technologies are providing underlie the current wave of discovery and growth in this novel discipline. This chapter is mainly concerned with methods for detecting and studying insects, birds, and bats flying in the open air, i.e. above the vegetation layer. Detection of these animals, and estimation of their numbers, can be achieved through in-flight capture or by remote sensing, with the latter comprising visual observation (including technologies for augmenting human sight), aural monitoring, radar, and laser/lidar. Remotely sensed animals can be identified, though sometimes only to a group of species, from characteristic features of the signals or images received. Information about the animals' activities-their mode of flight, orientation, etc.-can be obtained either by remote sensing or from sensors mounted on the animals. The latter method, which relies on radiotelemetry or archival logging to record the acquired data, may also be used to monitor the animal's physiological state, the environment it is moving in, and its trajectory. The chapter also examines how information about the timing and geographical extent of movements, and the environmental conditions the animals are experiencing, can be obtained. Finally, the particular challenges of observational aeroecology are identified, the multidisciplinary nature of the observing task is recognised, and some possible developments are proposed.