EFFECTS OF RADIO TRANSMITTERS ON MIGRATING WOOD THRUSHES

Authors

Larkin A. Powell, University of Nebraska-LincolnFollow
David Krementz, USGS, Patuxent Wildlife Research Center, Warnell School of Forest Resources, University of Georgia
Jason Lang, University of Georgia
Michael J. Conroy, USGS Cooperative Fish and Wildlife Research Unit

Document Type

Article

Date of this Version

1998

Citation

Journal of Field Ornithology 69:2 (1998), pp. 306-315.

Comments

This article is a U.S. government work, and is not subject to copyright in the United States.

Abstract

We quantified the effects of radio transmitters on Wood Thrushes (Hylocichla mustelina) using 4 yr of banding and telemetry data from Piedmont National Wildlife Refuge, Georgia. Flight performance models suggest that the 1.6-g transmitter shortens the migratory range of wood thrushes by only 60 km, and the estimated migratory range is adequate to accomplish migration even with limited fat stores. We used two strengths of line, 5- and 9- kg test-strength braided Dacron, to attach the transmitters using the thigh-harness method. We recaptured 13 returning radio-marked wood thrushes, seven of which were still marked. Six of the seven birds marked with the 5-kg test harnesses lost their transmitters within 1 yr while all six of the 9-kg test harnesses were still attached up to 21 mo later. Radio-marking did not reduce the return rates of adults and immatures, and the transmitters did not cause radio-marked birds to lose more mass than banded-only birds. Wood Thrushes can successfully carry a transmitter during migration with no detectable negative effects. We recommend continued use of the thigh-harness method, but we encourage the use of 5-kg cotton line.

Cuantificamos el efecto de los radiotransmisores en Hylocichla mustelina utilizando 4 arios de datos de anill~e y de telemetria del Refugio de Vida Silvestre Nacional de Piedmont, en Georgia. Los modelos de desemperio de vuelo sugieren que los radiotransmisores de 1.6-g reducen el alcance migratorio de esta especie por tan solo 60 km, y el alcance migratorio estimado es adecuado para conseguir la migracion inclusive con falta de reservas de grasa. Utilizamos lineas de dacron entrelazadas y probadas para resistencia de dos potencias de linea, de 5-y 9-kg, para ajustar los radiotransmisores utilizando el metodo de arnes de muslo. Recapturamos 13 aves marcadas con radiotransmisores, siete de las cuales estaban todavia marcadas. Seis de las siete aves marcadas con el arnes de 5-kg de prueba perdieron sus radiotransmisores el primer ano, mientras que las seis aves con los arneses de prueba de 9-kg los tuvieron consigo hasta 21 meses despues. Marcar con radio no redujo las tasas de retorno de adultos 0 inmaduros, y los radiotransmisores no causaron que las aves radio-marcadas perdieran mas masa que las aves que solo fueron anilladas. Individuos de Hylocichla mustelina pueden transportar radiotransmisores exitosamente durante la migracion sin algun efecto negativo detectable. Recomendamos el uso continuo del metodo del arnes en el muslo, pero recomendamos el uso de lineas de 5-kg de algodon.