RADIO TRANSMITTERS DO NOT AFFECT NESTLING FEEDING RATES BY FEMALE HOODED WARBLERS

--Few studies have examined the effects of radio transmitters on behavior, particularly of small passefines. Only recently have transmitters been made small enough for use on birds under 20 g. To determine if radio transmitters reduce activity levels, female Hooded Warblers (Wilsonia citrina) were fitted with transmitters while they were feeding nestlings. Females with transmitters and harnesses weighing 7-8.5% of body mass did not feed nestlings less frequently than did control females. Males mated to females with transmitters did not feed nestlings at different rates from males mated to control females. Brooding time and time spent perched on the edge of the nest did not differ significantly between tagged and control females. The finding that transmitters did not affect an energetically demanding activity such as feeding young suggests that other aspects of female behavior also were not adversely affected. USO DE RADIOTRANSMISORES NO AFECTA LA TASA DE ALIMENTACION DE PICHONES POR PARTE DE HEMBRAS DE W/LSON/A C1TRINA Sinopsis.--Pocos estudios hah examinado los efectos de radiotransmisores en la conducta de pequefios paserinos. Tan s61o recientemente los radiotransmisores e hah hecho lo suficientemente pequefios para ser ufilizados en aves de peso menor a los 20 g. Para determinar si los radiotransmisores reducen los niveles de actividad se le colocaron a hembras de Wilsonia citrina transmisores mientras 6stas estaban alimentando a pichones. Hembras con arneses y transmisores cuyo peso result6 set el equivalente entre 7-8.5% de su masa corporal no alimentaron a sus pichones con menor frecuencia que el grupo control. La pareja (machos) de las aves con transmisores tampoco alimentaron a los pichones con menor frecuencia que las parejas del grupo control. El fiempo de cubrir a los pichones, y el que pasaron posados en el borde del nido no fue significativamente diferente entre el grupo control y el experimental. E1 hecho de que los radiotransmisores no afectaron acfividades de alta demanda energ6tica (como alimentar a los pichones) en estas aves sugiere que otros aspectos de la conducta de las hembras tampoco fue afectada adversamente. Radio-tracking is useful for the study of animals that are shy or elusive. However, caution must be used when employing these techniques because radio transmitters may influence behavior (Kenward 1987). Some studies have demonstrated adverse effects of radio transmitters on birds including a reduction in flying (Hooge 1991), courtship behavior (Ramakka 1972), flight speed (Gessaman and Nagy 1988, Gessaman et al. 1991), foraging (Massey et al. 1988, Perry 1981), reproductive success (Croll et al. 1996), and nesting behavior (Massey et al. 1988) whereas other studies have shown minimal negative effects (e.g., Brigham 1989, Gilmer et al. 1974, Hill and Talent 1990, Morris and Burness 1992). In order to determine if transmitters adversely affect behavior, the study animal must be observed with and without the transmitter. However, the precise reason a radio-tracking study is undertaken is to explore behavior that is difficult to otherwise observe. One way to determine if transmitters negatively