Breeding Synchrony Best Explains Variation in Extra-Pair Mating System among Avian Species

Stutchbury used new data and a comparative pairwise test to confirm that there is a strong correlation between breeding synchrony and extra-pair fertilization (EPF) frequency in passerines, as first reported by Stutchbury and Morton. Although a pairwise test is a legitimate and powerful comparative method, Weatherhead and Yezerinac call for "better analyses to assess the correlation between synchrony and EPFs." There is a strong correlation between breeding synchrony and EPF frequency regardless of the comparative method used. Here I present a linear contrasts analysis on the 34 species given in Stutchbury using the phylogeny shown in Westneat and Sherman with other species added using the phylogeny in Sibley and Ahlquist.