Northern Cardinal microbiome pilot study 2020-2021

Animal populations can exhibit dramatic variation in individual fitness,
and microbiota are emerging as a potentially understudied factor
influencing host health. Bacterial diversity and community structure of
the gut microbiome are associated with many aspects of fitness in animals,
but relatively little is known about the generality of these relationships
in wild populations and non-mammalian taxa. We studied the Northern
Cardinal (Cardinalis cardinalis), a member of a taxon that is ecologically
important but underrepresented in microbiome research: songbirds. To test
for relationships between the microbiota and host fitness, we sampled the
cloacal microbiomes of wild cardinals and measured body condition index,
assessed the coloration of sexual ornaments (beak and plumage), and
collected blood to estimate the glucocorticoid response to stress. Both
alpha and beta bacterial diversity were related to individual variation in
body condition and several sexual ornaments, but not glucocorticoid
concentrations. Our results from a free-living songbird population add to
a growing body of research linking avian host fitness to internal
bacterial community characteristics. This study sets the stage for
manipulative experiments to determine how challenges to fitness and
microbiomes may upset these relationships.