Does frequent handling influence Eurasian whimbrel chicks’ body condition?

Collecting empirical data is essential for understanding the ecology and biology of a species. If the data collection procedure includes direct interaction with the study subject, particularly regarding repeated measures, there may be a risk of introducing biases on the collected dataset due to changes in the behaviour and/or physiology of the studied individuals. This can be particularly relevant during the breeding season when disturbance by researchers can affect birds on various aspects, including nest and chick survival, physiology, and chick body condition. Researcher effects on the chicks’ body condition have been shown in some species, but were apparently absent in others. Here, we investigate whether varying levels of handling influences the body condition of Eurasian whimbrel (Numenius phaeopus) chicks, using data collected on 88 individuals handled up to 11 times, during two breeding seasons. We found that neither the handling event (ordinal occasion when a chick was handled) nor the handling interval (period between two consecutive handling events) affected the chick’s body condition, but we found evidence that body condition is individually consistent during development. Hence, the levels of handling in our study did not have an apparent effect on Eurasian whimbrel chicks’ body condition. Although other potential effects may arise via researchers’ disturbance, our findings contribute to the discussion on researchers’ impacts on their study subjects, emphasizing the importance of species-specific evaluations to improve research methodologies and ethical practices.