An individual’s investment in constitutive immune defenses depends on both intrinsic and extrinsic factors. We examined how Leucocytozoon parasite presence, body condition (scaled mass), heterophil-to-lymphocyte (H:L) ratio, sex, and age affected immune defenses in golden eagle (Aquila chrysaetos) nestlings from three regions: California, Oregon, and Idaho. We quantified hemolytic-complement activity and bacterial killing ability, two measures of constitutive immunity. Body condition and age did not affect immune defenses. However, eagles with lower H:L ratios had lower complement activity, corroborating other findings that animals in better condition sometimes invest less in constitutive immunity. In addition, eagles with Leucocytozoon infections had higher concentrations of circulating complement proteins but not elevated opsonizing proteins for all microbes, and eagles from Oregon had significantly higher constitutive immunity than those from California or Idaho. We posit that Oregon eagles might have elevated immune defenses because they are exposed to more endoparasites than eagles from California or Idaho, and our results confirmed that the OR region has the highest rate of Leucocytozoon infections. Our study examined immune function in a free-living, long-lived raptor species, whereas most avian ecoimmunological research focuses on passerines. Thus, our research informs a broad perspective regarding the evolutionary and environmental pressures on immune function in birds.
This is the peer reviewed version of the following article:
MacColl, E., Vanesky, K, Buck, J. A., Dudek, B. M., Eagles-Smith, C, A., Heath, J. A.,...Downs, C.J. (2017). Correlates of immune defenses in golden eagle nestlings. JEZ-A: Ecological and Integrative Physiology, 327(5), 243-253
which has been published in final form at doi: 10.1002/jez.2081. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
Dudek, Benjamin M. and Heath, Julie A.. (2017). "Correlates of Immune Defenses in Golden Eagle Nestlings". JEZ-A: Ecological and Integrative Physiology, 327(5), 243-253. http://dx.doi.org/10.1002/jez.2081