Meeting Abstract
Animals that spend the summer in Utqiaġvik, AK (71°N, 156°W) experience 24h daylight for >2 months. Among species that experience these conditions are two migratory passerine birds, the Lapland longspur (Lapponicus calcarius, LALO) and the closely related snow bunting (Plectrophenax nivalis, SNBU). LALO nest in open tundra and can experience high rates of nest failure (~16% success, 2018), whereas SNBU are cavity nesters and have high fledging rates (~83% fledge, 2018). For this study, we were interested in whether these different predation pressures altered the daily rhythms in adrenocortical response. We hypothesized that LALO (exposed to high predation) would exhibit little to no hourly variation in adrenocortical response to stress compared with SNBU (low predation). Free-living birds of both species were captured throughout the polar day and blood samples were collected at <2 (baseline), 10, and 30 min post-capture. Plasma was assayed for corticosterone concentration using ELISA. For LALO, no discernible diurnal rhythm in corticosterone levels was detected. SNBU, however, showed a significant rhythm in baseline corticosterone levels (Circwave harmonic regression, p=0.02, f=4.09, r2=0.1007), but not in stress-induced levels. This study suggests that a lack of diurnal variation in ground-nesting LALO may represent an adaptation to the round-the-clock predation experienced at their nests.
