Meeting Abstract

P1.46  Friday, Jan. 4  The effects of Methimazole treatment on vernal migration, in White-crowned Sparrows PEREZ, JH*; WINGFIELD, JC; RAMENOFSKY, M; Univ. of California, Davis; Univ. of California, Davis; Univ. of California, Davis jhperez@ucdavis.edu

Each year billions of birds undertake migratory journeys to and from seasonal breeding grounds. This journey requires major changes in physiology, morphology and behavior governed by endocrine and neuro-endocrine mechanisms. However, the precise control mechanisms remain poorly understood. Prior research has suggested a role for thyroid hormones in the development and control of spring migratory behavior in Old World Passerines. Particularly in regards to the onset of migratory restlessness, a behavior considered to represent the urge to migrate in captive birds. Also, the thyroid plays an instrumental role in the control of photorefractoriness in European Starlings. Both sets of findings link the thyroid to photoperiodic functions which may be a clue to onset of migration. To begin to understand the role of thyroid hormones in migratory behavior of New World migrants, without the need to resort to surgical or radiological thyroidectomy we utilized the anti-thyroid agent Methimazole, which reversibly inhibits thyroperoxidase. This study explored the effects of continuous administration of Methimazole on the development of migratory condition and nocturnal restlessness in captive white-crowned sparrows (Zonotrichia leucophrys gambelii) following photostimulation with 18L:6D. Methimazole was administered via silastic implants. Here we present the effects of thyroid knockdown on three physiology and behavioral events associated with the development of migratory disposition: fattening, hypertrophy of the pectoralis muscles, and expression of migratory restlessness.