White Blood Cell Estimates Correlate to Measures of Population and Individual Health in an Endangered Population of Marbled Murrelet (Brachyramphus marmoratus)

Kelsey Ryan^1*Lindsay J Adrean²Matt Betts³Jonathan Dachenhaus³Jennifer Johns¹Miranda Michlanski¹S Kim Nelson⁴Shannon Phelps¹James Rivers³Daniel D Roby⁴Ethan Woodis³Brianna R Beechler^1*

• ¹Carlson College of Veterinary Medicine, Oregon State University, Corvallis, United States
• ²American Bird Conservancy, The Plains, Virginia, United States
• ³College of Forestry, Oregon State University, Corvallis, Oregon, United States
• ⁴Department of Fisheries and Wildlife, College of Agricultural Sciences, Oregon State University, Corvallis, Oregon, United States

White Blood Cells (WBCs) studied from blood samples are a valuable tool that can be used to assess health in wildlife and domestic animals at the individual and population levels, though are not commonly used in the study of wild seabird species. WBCs are involved in the immune response in the body, with levels changing in response to stress or infectious disease. Murrelets are a seabird species of conservation concern that are federally listed as threatened in multiple states across their range, thus necessitating the evaluation of their physiological health. We asked whether estimated WBC counts changed by measures of individual health (sex, L. marmoratii hemoparasite burden, body condition index) and population health (nesting propensity and year, with year representing changing environmental and ocean conditions) for the Oregon population of murrelet. We found that total WBC estimations were lower in years with better ocean conditions and higher nesting propensity. Male birds, birds less likely to nest, and birds with greater L. marmoratii burden had significantly lower estimated WBC counts, while birds with lower body condition index had elevated estimated WBC counts. Estimated WBC counts should be considered as a simple and inexpensive addition to research plans when studying wild seabird species.