COMPARATIVE ACCURACY OF AERIAL AND GROUND TELEMETRY LOCATIONS OF FORAGING RAPTORS

Widely ranging raptors are difficult to radio-track from fixed locatio ns on the ground; therefore, we investigated the feasibility of tracki ng Prairie Falcons (Falco mexicanus) from a Cessna 182 airplane outfit ted with a belly-mounted, rotary, H-antenna. Locations were estimated by flying directly over the signal's source. and recorded with an on-b oard global positioning system. Location estimates of stationary and m obile beacons derived from aerial tracking were more accurate than loc ations derived from triangulation by 4-6 ground-based trackers (xBAR 9 5% confidence ellipses: aerial = 112 ha, ground = 875 ha). Aerial accu racy was not influenced by mobility of a beacon and was similar for tw o observers. However, because falcons spend a majority of their time i n proximity of their aerie, most aerial fixes were close to the nest s ite. This resulted in significant underestimates of falcon foraging ra nges, especially for breeding males.