3.4.6 Bats in flight Field surveys of flying bats can incorporate one or more of four basic techniques. Direct observations of bats maybe made in the early evening or later by using spotlights or infrared night-vision scopes.
Captured bats maybe fitted with chemiluminescent tags so that individuals can be observed readily in the dark (Racey & Swift, 1985). Mist-nets or harp traps for capturing bats in flight can be useful in certain circumstances for survey work, but they are not recommended for general purpose use (see Chapter 4). Mist-nets are particularly useful in intensive small-scale studies when verification of species difficult to identify in flight is necessary. If mist-netting is to be used, the survey project must 3.4 LOC ATION OF KEY SITES AND FEEDING AREAS 35 be designed carefully to obtain the maximum benefit from the results obtained. Simply erecting nets on a casual or random basis rarely produces worthwhile results. Recent advances in portable ultrasonic detectors have led to bat detectors becoming invaluable tools with which to study bats. Their use to identify bats in flight is now widespread, although it is important to realise that the technique has its limitations.