Birds combined calls more than 11 million years ago

Multiple members of the tit and chickadee (= Parid) family combine two classes of calls, F and D, in a rigid order FD. In Japanese tits, FD has been argued on the basis of multiple experiments to involve syntax and non-trivial compositionality. How ancient are these call combinations? We show that FD combinations (as well as individual F and D calls) are present in nearly all Parid species, and almost absent in their closest relatives, the Remizidae and Stenostiridae. Using phylogenetic tools and ancestral reconstruction methods, we infer that FD combinations very likely emerged between 11 and 26 million years ago in the eastern Himalayas. This result contributes to evolutionary animal linguistics using a comparative phylogenetic approach to reconstruct the evolution of call combinations.