Focal Birds
LPS-focal and saline-focal birds did not differ in diet intake in terms of quantity of food consumed or macronutrient composition of food consumed (Figure 5, all P ≥ 0.480). Regardless of treatment group, focal bird body mass decreased over the course of the experiment (Figure S14, day: χ2 = 100.55, P < 0.0001), however, furcular fat scores were not influenced by treatment or time (Figure S15, all P ≥ 0.126). Body mass and fat score did not vary between male and female finches (sex: all P ≥ 0.282). Focal bird physiology was also not influenced by a cue of infection. Specifically, complement activity, baseline corticosterone concentrations, and testosterone concentrations did not vary by treatment or an interaction between treatment and time (Figure 6, all P ≥ 0.180). Additionally, complement activity and baseline plasma corticosterone concentrations did not vary between male and female finches (sex: allP ≥ 0.279). Regardless of treatment, testosterone concentrations (collected from males only) decreased over time (day: χ2 = 13.78P = 0.0002).
LPS-focal birds had lower bacterial richness (Figure S16; treatment: χ2 = 7.381, P adj = 0.018) than saline-focal birds, however this difference was already apparent prior to experimental treatment (Table S7). Shannon diversity did not vary significantly between treatments (χ2 = 2.938, P adj = 0.216). Regardless of treatment in the focal birds, higher fat consumption was associated with lower observed richness (Figure 7; χ2 = 7.242,P adj = 0.018) and although non-significant, there was a similar trend for lower Shannon diversity (Figure 7; χ2 = 6.356,P adj = 0.059). There was no significant effect of treatment (LPS-focal, saline-focal), sampling timepoint (day 0, day 5), or the interaction between treatment and time on any metrics of beta diversity in focal birds (Table S8, Figure S17; PERMANOVA, allP adj ≥ 0.464). Abundance of bacterial taxa at the phylum (Figure S18) or genus level (Figure S19) did not change over time in the control (saline-focal) treatment group (Table S9: allP adj ≥ 0.455) or in birds exposed to a social cue of infection (LPS-focal) when comparing pre- (day 0) and post-treatment (day 5) samples (Table S9: all P adj ≥ 0.838).