Long-term effects of repeated handling and bleeding in wild caught Great Tits Parus major

Abstract

Handling and bleeding are frequently used procedures in avian research and several studies show that they can exert short-term effects, such as elevation in corticosterone levels. However, the long-term effects of exposure to such manipulations are largely unknown, but could have important implications, especially for much of the long-term research on birds and experiments that involve longitudinal assessments. In this study, we evaluated the effect of handling and bleeding on some physiological and behavioural parameters. Hand-reared Great Tits Parus major originating from wild nests were used in two different experiments for other purposes. In these experiments, the birds were exposed to different frequencies of bleeding and handling events across a period of 45 days. The “high stress” group experienced a total of seven times handling and five times bleeding, while a “low stress” group was handled three times and bled only once. Thirty days after the experiments, when caught and handled from a cage, individuals of the high stress group were easier to catch, displayed significantly higher breath rates, and were more docile than individuals of the low stress group. No differences in body mass were detected. These results indicate that repeated manipulations cause evident long-term changes in coping with such procedures, which are likely due to learning effects, and provide empirical evidence that the past experimental history of an animal has to be taken into account in subsequent experiments.