Nocturnal bird migration and disrupted sleep/wake cycle
In most birds, changing photoperiods from winter to spring and from summer to fall have two consequences: increased feeding followed by migratory activity. To date, the neural system controlling the activation of migratory activity remains unknown, though behavioral observations point to a possible mechanism. During the migration season, diurnal songbirds show extensive disruption of their sleep/wake cycle, sleeping during the day and flying at night. In mammals, similarly altered cycles of activity result from blocking orexin expression in the hypothalamus. It is possible that decreased orexin expression is associated with migratory activity in songbirds. In addition, changes in ingestive behaviors and fuel availability may also be associated with disruptions in the sleep/wake cycles of migratory birds. The studies in my dissertation will address these issues through three main specific aims. First, I will determine that orexin systems are conserved in vertebrate brains. Second, I will test the association between orexin and migratory activity in songbirds. Third, I will confirm the association between fuel availability, orexin expression and migratory activity in songbirds.