The effects of human presence, restraint, and stressed neighbors on corticosterone levels in domesticated budgerigars ( Melopsittacus undulatus )

Limiting stress during interactions between captive animals and humans is important for effective husbandry. One physiological change during the vertebrate stress response is the release of glucocorticoid hormones. Here, we measured plasma corticosterone in female domesticated budgerigars ( Melopsittacus undulatus ) to test whether human presence, restraint, or removal and return of a newly stressed neighbor increases corticosterone. The presence of humans for 15 minutes at the beginning of the experiment did not significantly elevate corticosterone above baseline levels, suggesting that birds that acclimate to humans are minimally affected by their presence. However, at the end of the experiment after multiple blood sampling events, the same human presence test significantly elevated corticosterone above baseline and human presence levels measured at the beginning of the experiment. Thus, repeated blood sampling could cause progressively stronger stress responses to human presence. Restraint-induced corticosterone levels were significantly higher than all other treatments, indicating that human handling activates the stress response. After stressed birds were returned home, corticosterone levels of their neighbors were significantly higher than baseline at 25- and 45-minutes post-return. However, the 25- and 45-minute corticosterone levels were not significantly different from each other, or levels induced by human presence at the beginning or end of the experiment. This outcome suggests that social transmission of stress was limited across the sampled time frame. These data highlight the importance of evaluating the costs and benefits of different human-animal interactions in captivity, including in domesticated species that are more tolerant of forced proximity to humans.