Nest site correlates with nest type and body size in Troglodytidae passerines

Nest characteristics are highly variable in the Passeriformes, but the macroevolutionary patterns observable for birds in general are not necessarily valid for specific families, suggesting that both global and within-family studies are needed. Here, we used phylogenetic comparative methods to address the evolutionary patterns of nest type, nest site and habitat in the Troglodytidae, a passerine group with diversified nest and habitat characteristics. The common ancestor of the Troglodytidae likely constructed enclosed nests within sheltered sites (cavity or crevice), but the radiation of the group was characterized by (i) shifts to exposed nest sites (vegetation) with retention of enclosed nests or (ii) retention of sheltered sites with nest simplification (cup nests). Nest site and nest type presented strong phylogenetic conservatism and evolved interdependently, while habitat was poorly correlated with nest evolution. A phylogenetic mixed modelling approach showed that sheltered nest sites were associated with small body size, likely to avoid competition with other animals for these places. With these results, we improve the understanding of nest character evolution in the Troglodytidae and reveal evolutionary aspects not observed so far for passerine birds.