Levels of fecal corticosterone in sandhill cranes during a human-led migration

Fourteen captive-reared greater sandhill cranes (Grus canadensis tabida) were conditioned to follow ultralight aircraft to promote migration between Wisconsin and Florida (USA) after release. Fecal samples were collected throughout the training period in Wisconsin and during a 1,977-km human-led migration to Florida to determine fecal corticosterone (FC) concentrations by radioimmunoassay. The mean (±SE) FC concentration during the training period was 109.5±7.5 ng/g and was representative of baseline levels recorded previously from sandhill cranes. Fecal corticosterone concentrations increased in early migration compared to concentrations 1 mo prior to departure (P<0.01) but were not different from baseline concentrations at the end of the 6-wk migration period. The variability of FC concentrations in individual samples was greater throughout the migration than the training period. Increases in FC during migration were modest and generally consistent with normal corticosterone elevations observed in migrating birds.