Multistate mark-recapture analysis reveals no effect of blood sampling on survival and recapture of eastern kingbirds (Tyrannus tyrannus)

The experimentally supported and prevailing opinion is that blood sampling has few to no long-term effects on survival of birds when conducted properly, and blood sampling has become a vital addition to the toolbox of many ornithologists. However, many of the studies that concluded that blood sampling had negligible effects on birds used approaches that did not account for temporary emigration and probability of capture. To date, the only study to have done so found that blood sampling had a strong negative effect on survival. We conducted a mark-recapture analysis of 8 years of banding and bleeding data on Eastern Kingbirds (Tyrannus tyrannus) to determine whether survival was negatively influenced by blood sampling. Our analyses adjusted for temporary emigration and probability of recapture and accounted for (1) transitions between the bled and the nonbled state and (2) a change in protocol roughly midway through the study that resulted in a change from single to often multiple (and larger) draws of blood per year from single individuals. We found that survival rates of nonbled (0.61) and bled (0.67) males were statistically indistinguishable and that bled females had a higher probability of survival than nonbled females (0.68 and 0.58, respectively). The change to larger and more frequent blood samples was also not associated with a change in survival. Our data show that when accepted protocols were followed, blood sampling had no detectable influence on the survival of adult Eastern Kingbirds. Whether this applies generally awaits analyses using similarly rigorous methods on other species.