Meeting Abstract
Annually migratory birds express phenotypic flexibility in behavior, physiology and morphology that enable them to cope with dynamic changes in the energetic demands while progressing through each life history stage. In order for arctic bound migrants to perform long distance travel between wintering and breeding sites in spring, adequate fuel and power in flight muscles are required for sustained movements and resilience to the unpredictable conditions at high latitudes. In preparation for spring migration, Gambel’s White-crowned Sparrow (WCS) increase food intake, deposit lipid in subcutaneous stores and exhibit flight muscle hypertrophy prior to departure. Others have confirmed lipid deposition is expedited by molecular mechanisms to promote fatty acid mobilization and utilization in flight muscle. Yet progression of the biochemical and ultrastructual changes in flight muscle throughout the transitions from winter (Feb) and spring departure (April) on wintering grounds to arrival on arctic breeding sites (May) are not known. Our results confirm that each of the 3 stages is unique with intramuscular lipid peaking at departure (P<0.01), predominance of unsaturated fatty acids at departure and arrival (P<0.01) and concentration of intramuscular mitochondria greatest upon arrival (P<0.01). These results illustrate the fine-tuned flexibility of migrants at the subcellular level focusing on capacity for deposition and production of energy as WCSs progress from sedentary conditions in winter to impending mobility of migration and adjusting to unpredictable conditions on arctic breeding grounds.
