Effects of a common intestinal helminth on fecal corticosterone metabolite concentrations of Northern Bobwhite (Colinus virginianus)

It has been shown in several wild populations that helminths can affect survival and reproduction in avian hosts, even at moderate intensities. Colinus virginianus (Northern bobwhite) is a North American grassland game bird with a wide geographic range, including the southeastern and midwestern U.S. In the arid and semi-arid regions of its range, infections by the cecal worm Aulonocephalus pennula are common and frequently occur at high intensities. The objective of this study was to estimate changes in fecal corticosterone concentrations (FCMs) of C. virginianus as a function of A. pennula infection intensity. Wild C. virginianus were trapped in western Oklahoma using double-funnel traps in May and June of 2022 and 2023. We estimated A. pennula burden by extracting DNA from cloacal swabs and used a quantitative polymerase chain reaction (qPCR). We then estimated FCMs from C. virginianus fecal samples that had been defecated within 10 min of collecting the cloacal swab and FCM concentrations using an enzyme immunoassay recently validated for C. virginianus. The results show a significant increase in FCM concentrations with increasing A. pennula intensity. This study concludes that A. pennula influences the hypothalamus-pituitary-adrenal (HPA) axis by increasing FCM concentrations, and likely the concentration of circulating free corticosterone. Thus, there is a physiological mechanism by which A. pennula could impact both reproduction and survival of C. virginianus.