Performance and accuracy evaluation of small satellite transmitters

Recent technological advances have resulted in small (30 g) satellite platf orm transmitter terminals (PTTs) that can be used to track animals with mas ses as little as 900-1,000 g. While larger PTTs (>80 g) often yield locatio ns accurate to within hundreds of meters, the location accuracy of smaller PTTs has not been tested. We did these tests while using the PTTs to docume nt migration routes and nonbreeding areas of American peregrine falcons (Fa lco peregrinus anatum). We PTT-tagged 42 female peregrines from 2 breeding areas (upper Yukon River in eastcentral Alaska and Lake Powell on the Color ado Plateau in southern Utah and northern Arizona) late in the breeding sea sons of 1993-95. Only 2 of the PTTs failed prematurely (4.7% failure rate). Active PTTs (i.e., PTTs on live birds that eventually stopped transmitting due to battery exhaustion) averaged 280 transmission hours for 1993-94 (n = 3), 380 transmission hours for 1994-95 (n = 7), and 430 transmission hour s for 1995-96 (n = 15). Using an estimate of maximum ground speed of peregr ines (104 km/hr) based on empirical observations and aerodynamic calculatio ns, we determined that 4.48% of all locations provided to us by Argos (n = 2,323) were biologically implausible. We also received many poor-quality lo cations (68% of records were in Argos location classes 0, A, and B) typical of small, relatively underpowered PTTs. To estimate location accuracy of t hese poor-quality locations, we compared Argos-estimated locations with kno wn locations of 11 rock doves (Columba livia) tagged with PTTs. The locatio n types with the highest precision averaged 4 km from the true location, wh ile the location types with the lowest precision averaged 35 km from the tr ue location. These results indicate the PTT locations were sufficient to do cument animal movements over broad spatial scales such as identifying migra tion routes and nonbreeding areas of birds. This technology is more efficie nt and less biased than the current approaches used to obtain this informat ion (mark-resighting of banded animals or standard radiotelemetry technique s). However, the PTTs currently available are not suitable when position ac curacy <35 km is needed.