Baseline and Stress‐Induced Plasma Corticosterone during Long‐Distance Migration in the Bar‐Tailed Godwit,Limosa lapponica

Abstract

The specific roles of corticosterone in promotion of avian migration remain unclear even though this glucocorticosteroid is elevated in many migrating bird species. In general, glucocorticosteroids promote metabolic homeostasis and may elicit effects on feeding and locomotion. Because the migratory stages of refueling and flight are characterized by distinct behaviors and physiology, the determination of corticosterone levels during each stage should help identify potential processes in which corticosterone is involved. We measured baseline levels of corticosterone in bar-tailed godwits (Limosa lapponica) during two distinct stages of migration: (1) immediately after arrival at a false stopover site just short of the Wadden Sea and (2) throughout the subsequent 4-wk refueling period on the Wadden Sea. Plasma corticosterone was higher in arriving than in refueling birds. In addition, corticosterone increased with size-corrected body mass during the refueling phase, suggesting that corticosterone rises as birds prepare to reinitiate flight. Therefore, elevated corticosterone appears associated with migratory flight

Role of the Low‐Affinity Glucocorticoid Receptor in the Regulation of Behavior and Energy Metabolism in the Migratory Red KnotCalidris canutus islandica

“…Consistent with previous work described in Piersma et al (2000), baseline levels of plasma corticosterone in spring birds were elevated in association with the peak in body mass at the time when wild conspecifics typically initiate migratory flight. However, as in other migrating species (e.g., Schwabl et al 1991;Gwinner et al 1992;Romero et al 1997;Tsipoura et al 1999;Mizrahi et al 2001;Landys-Ciannelli et al 2002), plasma corticosterone in red knots was not elevated to maximal stress concentrations. Thus, if corticosterone participates in the regulation of migration, it probably does so at an intermediate level (reviewed in Landys 2003).…”

“…Periods of migratory fueling are characterized by relatively low corticosterone levels (Landys-Ciannelli et al 2002;Landys et al 2004b). Even in the red knots examined here, plasma corticosterone was comparatively lower during mass gain than during mass peak.…”

“…As shown in other species (Landys-Ciannelli et al 2002;Landys et al 2004b), migrating red knots Calidris canutus islandica display elevated levels of corticosterone specifically in association with the substage of migratory flight. For example, when held in captivity on their wintering grounds, red knots show an increase in plasma corticosterone only after having attained a body mass similar to that of departing conspecifics (Piersma et al 2000).…”

“…Corticosterone appears to increase specifically in association with migratory flight (Landys-Ciannelli et al 2002;Landys et al 2004b) and therefore may promote processes associated with this substage of migration, such as migratory activity and energy mobilization. Such a prediction is consistent with past research (Dolnik and Blyumental 1967;Meier and Martin 1971), in which corticosterone was shown to contribute to the regulation of migratory restlessness, the intense and persistent movements that characterize birds in a migratory condition.…”

“…This technique often elevates glucocorticoid levels to pharmacological concentrations (Gray et al 1990;Astheimer et al 1992) that may misrepresent stage-specific levels. During migration, elevations in plasma corticosterone are only slight and do not approach maximal concentrations (e.g., Schwabl et al 1991;Gwinner et al 1992;Romero et al 1997;Tsipoura et al 1999;Mizrahi et al 2001;Landys-Ciannelli et al 2002;Landys et al 2004b). Landys et al (2004a) recently examined the role of corticosterone in the migratory Gambel's white-crowned sparrow Zonotrichia leucophrys gambelii.…”