PATTERNS OF CORTICOSTERONE SECRETION IN MIGRATING SEMIPALMATED SANDPIPERS AT A MAJOR SPRING STOPOVER SITE

• Published in: The Auk 2001-01, Vol.118 (1), p.79-91
• Main Authors: Mizrahi, David S, Holberton, Rebecca L, Gauthreaux, Jr, Sidney A
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal migration behavior; Animal, plant and microbial ecology; Animals; Autoecology; Aves; Biological and medical sciences; Bird migration; Birds; Body fat; Corticosterone; Fundamental and applied biological sciences. Psychology; Hormones; Metabolism; Nutrient reserves; Physiology; Sandpipers; Seasonal migration; Secretion; Spring; Stress; Stress response; Thermoregulation. Hibernation. Estivation. Ecophysiology and environmental effects; Vertebrata; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 0004-8038; 1938-4254; 2732-4613
• DOI: 10.1642/0004-8038(2001)118[0079:POCSIM]2.0.CO;2

Seasonal changes in corticosterone metabolism may be in part responsible for mediating the changes in nutrient reserves before and during migration. To investigate the role of glucocorticoids in the migratory physiology of Semipalmated Sandpipers (Calidris pusilla), we compared plasma levels of corticosterone in response to capture and handling stress during prolonged stopovers in Delaware Bay during spring 1996 and 1997. Although Semipalmated Sandpipers showed significant stress responses to handling in both years, the magnitude of the response was significantly lower in 1997. We found no correlation between energetic condition and initial corticosterone concentration in either year, or between energetic condition and corticosterone concentration in samples collected 30 min after capture in 1996. However, energetic condition was positively correlated with corticosterone concentration in 30 min sample collected in 1997. Between-year differences in regression functions of energetic condition by Julian date suggested that birds were accumulating fat mass more rapidly, or arriving in better energetic condition during 1996 compared to 1997. Those differences were especially evident during the “early” stages (before 26 May) of stopover periods. In 1997, we found that birds sampled early in the season did not show a significant increase in corticosterone 30 min after capture, while birds sampled in early 1996 did. In both years, birds sampled during the “late” stages of stopover periods (after and including 26 May) showed significant stress response. Birds in relatively poor energetic condition, or with low rates of fat-mass gain, were less likely to secrete additional corticosterone in response to acute stress, possibly to protect skeletal muscle needed for migratory flight. Those results suggest that patterns of corticosterone secretion in sandpipers can be modified in response to changes in energy demand during the migratory period.