Nutrient content of Northern bobwhite arthropod prey collected in Western OK

Insectivores gain macronutrients and elements from consuming arthropod
prey, but must also deal with indigestible components (i.e., exoskeleton)
of prey. For example, avian chicks (e.g. northern bobwhites; Colinus
virginianus) have limited gut space, and ingesting prey with relatively
higher proportions of indigestible components may impact assimilation
efficiency, growth, and survival. The ability of insectivores to choose
higher quality prey would depend on prey taxa varying consistently in
nutritional content. We tested if there were consistent differences among
taxonomic orders of arthropod prey in their macronutrient (protein and
lipid), elemental (C and N), and exoskeleton content. We used northern
bobwhite chicks as our focal insectivore and focused on their potential
prey as a case study. We also tested the influence of indigestible
exoskeleton on the measurement of macronutrient content and the ability of
elemental content to predict macronutrients. We found large and consistent
variation in macronutrient and elemental content within and between
arthropod orders. Some orders had consistently high protein content and
low exoskeleton content (i.e., Araneae) and are likely higher quality prey
for insectivores. Abundant orders common in the diets of insectivores,
like Hymenoptera and Coleoptera, had high exoskeleton content and low
protein content. We also found support for the ability of elements to
predict macronutrients, and found that metabolizable (i.e. exoskeleton
removed) elemental content better predicted macronutrient content. A
better understanding of arthropod nutrient content is critical for
elucidating the role of spatial and temporal variation in prey communities
in shaping the growth and survival of insectivores.