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.

Methods
Full details of data collection are available in the associated paper.

Data in 'sticky strips analysis 2018' were collected by repeated sampling (collections A:D) of fleas and mesostigmatid mites in nests ('cavities') in two experimental conditions.

Data in 'PUMA_metadata_nestlevel' were collected by observing nest progress and fledge rate for purple martin nests in two experimental conditions ("Changes" and "No_changes")

Data in 'mass_2016_2017_2018' were collected by weighing purple martin nestlings at the time of banding (Date_1, Mass_1) and (for a subset of nests) again prior to fledging (Date_2, Mass_2) in nests in two experimental conditions ("C" and "E")

Data in 'full_blood_data.csv' were collected by blood sampling purple martin nestlings and measuring hematocrit, triglyceride, uric acid, H:L and leukocyte count, along with biometric measurements such as nestling mass, age and clutch size.