Meeting Abstract
10.5 Thursday, Jan. 3 Hormonal correlates and thermoregulatory consequences of molting on metabolic rate in a northerly wintering shorebird VEZINA, F.**; GUSTOWSKA, A.; JALVINGH, K.M.; CHASTEL, O.; PIERSMA, T.; NIOZ Royal Netherlands Institute for Sea Research, The Netherlands; Avian Ecophysiology Unit, Department of Vertebrate Ecology and Zoology, Gdansk University, Poland; NIOZ Royal Netherlands Institute for Sea Research, The Netherlands; CNRS Centre d’�tudes biologiques de Chiz�, France; Animal Ecology group, Centre for Ecological and Evolutionary Studies, University of Groningen, The Netherlands fvezina@nioz.nl
We studied the energetic investments and variations in plasma levels of thyroid hormones associated with prebasic molt in outdoor captive red knots (Calidris canutus islandica), a northerly wintering shorebird that spends the non-breeding season on wind and rain exposed European mudflats. Red knots exhibited a 10% increase in average mass-corrected basal metabolic rate (BMR) during molt compared to summer and winter levels; this yielded an estimate of 16% for molting efficiency. During feather renewal, molting rate of body feathers was positively correlated to plasma levels of thyroxine (T4), showing that not only T4 is related to body molt, but that it is also related to its duration. Furthermore, body feather molting rate was positively correlated with thermal conductance, indicating that birds molting the fastest were loosing more body heat. Across seasons, triiodothyronine (T3), a known metabolic stimulator responding to ambient temperatures, was correlated to thermal conductance and BMR. We suggest that the thermoregulatory consequences of avian molt results in elevated plasma levels of T3, which in turns lead to upregulation of BMR in a fashion similar to the acclimatization response to cold known in this and other species. This interpretation is supported by a positive relationship between the individual change in conductance and the change in BMR from summer to the molting period.
