Corticosterone levels in sub-adult and family groups of whooping cranes (Grus americana) in wintering locations of Lamar Peninsula, Texas

Whooping cranes (Grus americana) are endangered species recovering from a critical population number of less than 20 individuals in the 1930's. Former (e.g., habitat loss) and potential new threats (e.g., human activities), especially in wintering grounds, may affect whooping crane population recovery. Thus, it is important to determine a possible method to assess physiological health of the wild population using a non-invasive technique. This study evaluated, for the first time, fecal corticosterone (CORT), a stress hormone in birds, in the wild population of whooping cranes. We measured fecal CORT levels of two sub-adult flocks in 2010 and 2011 and two family groups in 2011 in three different locations on Lamar Peninsula and one site in Holiday Beach, Texas. For sub-adult groups, there was significant difference in CORT between groups (P < 0.001). CORT levels of sub-adults in 2010 tended to increase over time. The sub-adult group in 2011 showed higher mean fecal CORT after three collection dates at the end of March, 515.65 +/- 124.53 ng/g (mean +/- SE). For family groups, there was no significant difference in CORT between groups (P = 0.79). However, we observed a positive relationship of fecal CORT with time of year for Family 2, but not for Family 1. Human activities, pre-migration, or environmental differences could be factors affecting the production of CORT in wild whooping cranes. More frequent samples from the same whooping crane groups would be needed to identify potential contributing factors. This study presents helpful new information of whooping cranes using off-refuge sites that may aid in the decisions of habitat selection for reintroduction of whooping cranes.