A parasite reduction conservation intervention does not improve fledging success or most condition metrics for purple martins

Purple Martins (Progne subis subis) have an unusually close relationship
with humans, as they nest exclusively in man-made nest boxes. Current
conservation policy directly promotes further interaction with this
species by advocating regular replacement of nest materials during the
nestling phase to reduce ectoparasite load and increase nestling fitness.
We conducted the first test of the efficacy of this recommendation and
found that it was partially effective in reducing parasite abundance, but
had no effect on nestling fledging success, body mass, leukocyte count, or
triglyceride or uric acid concentration. We found a small but significant
increase in nestling hematocrit associated with nest material replacement,
implying that parasites may induce nestling anemia. Contrary to our
expectations, we also found elevated heterophil/lymphocyte ratios in
nestlings with replacements, possibly indicating elevated physiological
stress associated with nest replacements. Based on our results, we do not
recommend nest material replacements to combat routine parasite
infestations.