Meeting Abstract

P1.152  Tuesday, Jan. 4  Effect of melatonin manipulation on circadian behavior and reproduction in a wild bird GREIVES, TJ*; BELTRAMI, G; HAU, M; Max Planck Institute for Ornithology, Vogelwarte Radolfzell, 78315 Radolfzell, Germany; University of Ferrara, 44121 Ferrara, Italy tgreives@gmail.com

Nearly all organisms display circadian rhythms, and these rhythms are thought to enhance fitness by facilitating proper timing of behavioral and physiological events with environmental conditions. The majority of studies on circadian rhythms however have been conducted in the lab, where the fitness relevance of endogenous rhythms cannot easily be determined. The pineal hormone melatonin is an important component for the entrainment of circadian rhythms with the organism’s environment. The current study aimed to begin to uncover the effects of disrupting endogenous circadian rhythms via manipulation of the melatonin rhythmicity in a free-living vertebrate. Prior to the onset of the egg-laying, wild great tits (Parus major) received a silastic implant either left empty or filled with melatonin; this manipulation is known to abolish diel melatonin rhythms by elevating daytime levels to levels comparable with the night peak of melatonin in control birds. Additionally, all individuals received a small radio-transmitter (<0.5g). Using an automated telemetry-recording unit, we recorded the precise timing of onset of daily behavioral activity, as well as the total amount of activity per day from all individuals. Focal individuals were followed throughout the breeding season and measures of reproductive success were assessed. The data presented will shed light on the significance of circadian rhythms in the wild.