Phylogenetic and functional trees
As a basis for all subsequent phylogenetic analysis, we prepared a phylogenetic tree for the species in our community by trimming from the original phylogeny available from www.birdtree.org (Jetz et al. 2012; Fig. S2). Jetz et al. (2012) constructed this ‘backbone tree’ using genetic data from 6693 species of birds using 15 genes (19 loci) of 151 key species that were time-calibrated with ten well-known fossils (Jetz et al., 2012). We used the R packages “ape” and “phytools” (Paradis et al. 2004; Revell 2012) to obtain a consensus tree for our 15 target species using a pseudo-posterior distribution (https://birdtree.org/subsets/) from 1000 random samples from the ‘backbone tree’ after applying the 50% majority rule (i.e., the proportion of a split to be present in all trees) prior to modelling inter-specific variation across the phylogeny.
Bird species were classified into a functional tree using the quantitative morphological traits and qualitative feeding traits collected from Ali and Ripley (1968). We used “gower” distance to calculate the pair-wise distances between species while the UPGMA clustering method was used to convert the species-wise trait distances into branches in which the species formed the tips labelled with the aid of the “phangorn” package (Schliep 2011).