Table 1

Characteristics of males that predicted their rankings by females under UV+ and UV− conditions, shown separately for morphometric variables and plumage reflectance spectra

Trait UV+ ranking predictor UV− ranking predictor
Statistic P Statistic P
MassF =  0.58NSF =  1.00NS
Fat scoreS =  2.33NSS =  1.39NS
Length of tarsusF =  0.27NSF =  1.12NS
Length of 8th primaryF =  2.75NSF =  0.11NS
Asymmetry of tarsusS =  0.28NSS =  1.88NS
Asymmetry of 8th primaryK-W H =  3.15NSK-W H =  1.19NS
Throat feathers with white tips, %S =  3.12NSS =  4.86NS
Covert feathers with white tips, %S =  3.67NSS =  3.67NS
Bill black, %S =  0.19NSS =  0.10NS
TraitUV+ ranking predictor Summary
Wilk’s λ P meanPC1PC2PC3
Throat0.308<‡0.60preferred males have high “violet” and  “red” relative to UV and “green”
Throat tips0.071<0.012.724.03*0.225.48†preferred males “whiter”
Covert tips0.616NS0.400.582.47NS
UV− ranking predictor
Throat tips0.512NS0.681.110.550.79NS
Covert tips0.585NS0.100.072.31NS
  • Throat and coverts refer to the main iridescent region of the throat and wing covert feathers, respectively; tips are their white/brown margins. In all cases, the independent variable is rank, with four levels (1 = most preferred, 4 = least preferred). Morphometrics: Variables are compared by univariate tests. S refers to Friedman’s nonparametric repeated-measures ANOVA (15), with the males’ quartet as the blocking factor. Because primary feather asymmetry had too many missing values (due to abrasion of tips) for Friedman’s test, Kruskal–Wallis’ nonparametric ANOVA was used (15) as if males were independent. For repeated-measures ANOVA F tests, df = 3,21; for Friedman S and Kruskal–Wallis H, df = 3. Spectrophotometrics: Plumage variables are compared by repeated-measures MANOVA and ANOVA with 10 replicate feathers per region per bird (measurement details in legend of Fig. 3). For the UV+ rankings, mean reflectance and principal components (PC) are calculated from the full avian visible range (300-700 nm); for the UV− rankings, they are calculated for the human visible range (400-700 nm). Principal components were calculated from standardized reflectance measurements (mean reflectance subtracted) such that PC1 is the first component of spectral shape rather than a correlate of mean reflectance. Only PCs explaining >5% of the spectral variation are included. Wilk’s λ tests the mean reflectance and main PCs together by repeated-measures MANOVA, with ∗, P < 0.05;  

  • , P < 0.01; and  

  • , P < 0.001. Only where Wilk’s λ is significant should the univariate F tests for each dependent variable be consulted; for Wilk’s λ, df = 12,47.