Table 1.
Summary of key findings
| Age category | Dependent variable | Independent variables | Effect |
|---|---|---|---|
| Developmental | Beak color 50 DPH | Yng Trt | Yng Trt = KLH birds had reduced % beak redness |
| Δ Beak color (50–65 DPH) | Day × Yng Trt | All beaks got redder, rate of increase higher for Yng Trt = KLH | |
| Adulthood | Baseline adult Ab (LPS) | None | None |
| Δ Adult Ab (LPS) | None | None | |
| Baseline adult Ab (KLH) | None | None | |
| Δ Adult Ab (KLH) | Day × Yng Trt | KLH Ab levels increased from pre- to post-adult KLH challenge, rate of increase was greater for Yng Trt = KLH birds | |
| Baseline adult beak color | Yng Trt | B2, S1R, ΔL affected by Yng Trt = KLH; B2 and S1R values indicated less red color in the beaks for Yng Trt = KLH, and there was significant difference in beak color space (ΔL) for those birds compared to Yng Trt ≠ KLH | |
| Δ Adult beak color pre- to post-LPS | None | None | |
| Δ Adult beak color pre- to post-KLH | Day, Yng Trt × Δ Adult Ab (KLH) | B2, S1R, S1U, H4b, ΔL, ΔS all changed from pre- to post- KLH challenge (becoming less red); ΔB2 and ΔS1R were inversely related to ΔKLH Ab |
Major findings for each dependent variable of interest. During development, the percent of an individual zebra finch’s beak that was red was assessed at 50 days posthatch (DPH) and again at 65 DPH. Young treatment (Yng Trt) was KLH, LPS, or control. The change in percentage red (Δ Beak color) was assessed from 50–65 DPH. When birds were at least 3 years old, they were challenged with LPS and 3 weeks or more later, with KLH, and both beak coloration and antibody (Ab) levels were assessed prior to (baseline) and following (4 days for LPS; 8 for KLH) each immune challenge. For measures of adult beak coloration, we used tristimulus color parameters and avian color vision model metrics: B2 is a measure of brightness, S1R is a measure of saturation or chroma at high wavelengths, S1U is saturation at low wavelengths, H4b is hue, ΔL is achromatic contrast, and ΔS is chromatic contrast.