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Table 2 Factors affecting bill surface area of 36 species of passerine from the Meliphagoidea

From: Spatial variation in avian bill size is associated with humidity in summer among Australian passerines

  Wald statistic Df p-value parameter SE
(Intercept) 2354.543 1 <0.001 5.768 0.559
Wing Length 656.986 1 <0.001 0.01145 0.00056
SeasonCapture.autumn 49.425 3 <0.001 0 NA
 .winter   −0.00958 0.00543
 .summer   0.03092 0.00758
 .spring   0.01419 0.00543
Sex.female 59.914 1 <0.001 0 NA
 .male   0.02894 0.00423
YearCapture 10.097 1 0.001 −0.00089 0.00027
Humidity 66.511 1 <0.001 0.01802 0.00765
Tmax 0.514 1 0.473 0.00386 0.00743
Rain 0.668 1 0.414 −0.00058 0.00042
Humidity2 0.435 1 0.510 0.00048 0.0002
Tmax2 0.414 1 0.520 0.00012 0.00014
Rain2 0.239 1 0.625 6.28E-07 5.41E-07
Humidity * Tmax 4.284 1 0.038 −0.00085 0.00027
Humidity*Rain 0.491 1 0.483 −0.00004 0.00002
Tmax * Rain 5.250 1 0.022 0.00004 0.00002
Variance of random effects Component SE  
Region 0.000502 0.000158  
YearCapture 0.000163 0.0000821  
Species 0.1485 0.0360  
Residual 0.008474 0.000230  
  1. Results are from a full mixed model of bill size (log-transformed) with fixed effects of body size (wing length), season of capture, sex and all weather variables and their interactions and quadratic terms, and random effects of species, IBRA region, year and residual effect (see Model 1 in Methods). The table shows Wald statistics, df, p-values, parameter estimates and standard errors (SE). Tmax is the mean maximum summer temperature; humidity is mean summer water vapour pressure (hPa), and rainfall is mean summer rainfall, all averaged for the preceding 5 summers prior to capture; summer is defined as the months December to February. Parameter estimates for Season of Capture are relative to autumn, and for Sex are for males relative to females. Log-likelihood of model = 5102.48. N = 2864 individuals, across 41 years, 36 species and 77 IBRA regions. Significant weather terms (p < 0.05) are shown in bold