Meeting Abstract
The mammalian gut microbiome is important to food utilization, nutrient recycling, fattening, and overall host health in addition to being implicated in stress-responsiveness and anxiety-like behavior. The bird microbiome has been understudied, and hummingbirds have been cited as an important study system because of their rapid metabolism, nectarivory, and high sucrase activity. Additionally, some fatten seasonally for annual long-distance migration (e.g., rufous hummingbird, Selasphorus rufus) whereas others (e.g., Anna’s hummingbird, Calypte anna,) are year-round residents undergoing much smaller annual changes in fat stores. Rufous and Anna’s hummingbirds were captured in the San Juan Islands (WA, USA) from May through August, weighed and scored for fat accumulation; cloacal fluid (CF) and feces were collected opportunistically (at known times post-capture) in microcentrifuge tubes. OTUs were identified from the V3-V5 region of 16s rDNA to approximately species level. Core microbiota (phyla present in > 95% of samples) included Actinobacteria, Proteobacteria, Cyanobacteria, and Firmicutes, but not Bacteroidetes. The relative abundance of 6 bacterial phyla varied with fat score, but the ratio of Bacteroidetes to Firmicutes, commonly found to vary with obesity in mammals, did not, perhaps because of rapid cycling of fat score within the migratory phase. Despite compositional differences, however, the predicted functional profiles of hummingbird gut microbiomes were largely conserved, indicating that compositionally distinct microbiomes can maintain similar functions. Further analyses will examine relationships among species, annual phase, fat score, fecal microbiota structure, CF corticosterone, and tonic immobility, a potential behavioral correlate of stress responsiveness.
