Figure 2.

Stress-induced corticosterone (CORT) in superb starlings measured over 3 years. Mean±s.e. stress-induced CORT in (a) 2005, (b) 2003 and (c) 2004 measured over a stress series from 3, 10, 30 and 60 min (and 90 min in 2005) after capture. Birds that became breeders (open squares), helpers (closed circles) and non-breeders/non-helpers (open triangles) had similarly shaped curves. Years are arranged according to the amount of rainfall received during the pre-breeding period (table 1). In 2005, the driest of the 3 years where stress-induced CORT was measured, birds that became helpers had significantly higher stress-induced CORT than those that became breeders and non-breeders/non-helpers. There were no differences in stress-induced CORT between birds that became breeders, helpers or non-breeders/non-helpers in the other 2 years. Sample sizes for birds that became breeders (B), helpers (H) and non-breeders/non-helpers (N) are indicated at the bottom of each panel.