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Linking Gut Microbiomes and Health in Northern Cardinals
Microbiomes play a crucial role in the health of living organisms, encompassing both beneficial and detrimental microbes. The diversity of these microbial communities is fundamental to overall well-being; low diversity can result in immune dysfunction and ineffective nutrient absorption, while a rich variety of microbes tends to enhance resilience against stress and pathogens.
In an effort to delve deeper into this matter, researchers at Florida Atlantic University’s Charles E. Schmidt College of Science have conducted a five-year investigation into the interplay between gut microbiomes and various health-related traits in songbirds. While laboratory studies have established connections between gut microbiomes and physical traits in captive species, knowledge about these relationships in wild animals, particularly birds, remains limited.
The study, featuring the Northern cardinal (Cardinalis cardinalis), a familiar sight in many backyards, marks a significant advancement in this area. Renowned for their eye-catching red feathers and unique characteristics—such as a striking red beak and a black facial mask—these birds served as the perfect subjects to explore how their gut microbiomes are associated with physical attributes related to health and reproductive success.
Published in the journal Oikos, the findings indicate that the diversity of a cardinal’s gut microbiome correlates with its physical condition and the quality of its ornamental traits, such as plumage and beak color. “Our results substantiate the idea that a wild bird’s health is interlinked with its microbiome, with male ornamentation potentially serving as an indicator of health,” stated Rindy Anderson, Ph.D., the study’s senior author and an associate professor in the Department of Biological Sciences at FAU.
The Northern cardinal, which utilizes carotenoid pigments for its vivid colors, presented an ideal case study. These pigments are directly tied to the health and genetic quality of the individual bird, as their vibrant coloration can signify overall fitness.
“This research holds significant implications for the field of conservation biology, enhancing our comprehension of how to promote animal health in various contexts, including wildlife rehabilitation centers, zoos, aquaria, and captive breeding initiatives for threatened species,” explained Morgan Slevin, the lead author and a Ph.D. candidate at FAU.
To investigate the connections between microbiota and host fitness, researchers collected cloacal microbiome samples from wild Northern cardinals and evaluated their body condition index, ornament coloration, and stress glucocorticoid levels through blood samples. The study aimed to elucidate the microbiota-gut-brain axis in natural songbird populations, documenting relationships among multiple facets of this complex system.
Slevin noted, “There is a clear positive correlation between the redness and saturation of cardinal ornaments and individual quality. Deeper red coloration signifies enhanced carotenoid presence, which we found to relate directly to microbiome diversity.”
Both alpha and beta diversity metrics of the gut bacteria were associated with variations in individual body condition and sexual ornaments, although no link was found with glucocorticoid levels. Interestingly, the saturation of the beak color was also related to beta diversity, suggesting flock members with similar beak coloration profiles tended to have comparable gut microbiome structures.
“While we hypothesized that birds exhibiting maximal beak saturation would be the highest quality individuals, our findings indicate that the presence of a diverse microbiome might come at the expense of beak coloration saturation,” Slevin added.
These revelations from a natural Northern cardinal population contribute to an expanding corpus of research linking health traits in birds with their underlying microbial ecosystems.
“Our study, along with future investigations, is poised to further clarify whether a bird’s gut microbiome can serve as a reliable predictor of its individual quality,” concluded Anderson.
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