Birds after dark:: an efficient and inexpensive system for making long-range observations at night

The ability of investigators to study the behavior of animals at night is often limited by the difficulties of making observations in the dark, particularly at a distance. Indirect techniques, such as radio tracking, generally produce limited behavioral data, and most night-viewing equipment tends to be both inefficient for making long-range observations and expensive. We describe a long-range night-vision system consisting of a camcorder and infrared laser illuminators. We tested the performance of this system by comparing our ability to quantify the foraging behavior of shorebirds during the day and at night. Distance thresholds for detecting ingestion of prey and for identifying them were similar during the day and night for all species. At night, we were able to quantify all foraging parameters for all species at distances up to 59 m, and to count pecks and steps at distances greater than 200 m for some species. The observation system we describe can be further improved by using camcorders with higher optical zooms or more powerful infrared laser illuminators. Because of its efficiency and relatively low cost, this system has the potential for being useful in many other applications that require long-range observations of animals at night.