Correlates of immune defenses in golden eagle nestlings

• Published in: Journal of Experimental Zoology Part A: Ecological and Integrative Physiology
• Main Authors: MacColl, Elisabeth, Vanesky, Kris, Buck, Jeremy A., Dudek, Benjamin M., Eagles‐Smith, Collin A., Heath, Julie A., Herring, Garth, Vennum, Chris, Downs, Cynthia J.
• Other Authors: U.S. Bureau of Land Management, National Science Foundation, Boise State University, Division of Biological Infrastructure
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2017
• Subjects: Aquila chrysaetos; golden eagle
• Online Access: http://dx.doi.org/10.1002/jez.2081; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjez.2081; https://onlinelibrary.wiley.com/doi/pdf/10.1002/jez.2081; https://onlinelibrary.wiley.com/doi/full-xml/10.1002/jez.2081; https://onlinelibrary.wiley.com/doi/am-pdf/10.1002/jez.2081

Abstract 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.