Pagel’s Lambda
To assess whether our traits contained phylogenetic signals, Pagel’s lambda was calculated for bird weight and for each alpha diversity metric in each dataset. Bird weight was always significantly different from 0 (p <0.0001) and lambda was between 0.9 and 1.0 (Supplemental Table S3). The exception was the Passeriformes-only gizzard dataset (lambda = 0.63, p =0.27), but we note that this dataset has extremely low sample size (N=9 individuals from 8 species).
Five microbiota diversity lambdas were significantly different from zero in the full dataset: Blood-observed, Blood-Shannon, Buccal-Shannon, Intestines-Shannon, Intestines-Simpson (Table 1). Three were significantly different from zero in the Passeriformes-only dataset: Buccal-observed, Buccal-Shannon, Cloaca-observed (Table 1).