Conservatism and divergence in communication systems: sound signals of shorebirds and woodpeckers

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Animal sounds are diverse and have diverse functions and applications. Sounds are widely used in conservation and management to detect or monitor different species, including rare and endangered species. Woodpeckers for example, strike trees with their bills to attract mates or announce territorial claims (drumming"). Biologists can use these loud drumming sounds to determine presence and abundance of different woodpecker species. Common reasons for sounds of different species to be unique are (1) requirements to efficiently identify members of the same species, and (2) rapid divergent evolution between populations when they are separated geographically by some barrier, such as a mountain range. Recent research has surprisingly shown that many animal sounds have evolved extremely slowly. An example is shorebirds, a group that arose in the time of dinosaurs, but that shows many similarities in voice even between distantly related species. The proposed program of research will investigate how sound displays differ among different species of shorebirds and woodpeckers, and how these differences fit into the bigger picture of evolutionary conservatism over millions of years. Do these sounds evolve slowly because the organ of voice ("syrinx") is very simple? Do different calls in the display repertoire evolve together as a set, because all are produced by a single vocal organ? If so, particular qualities should pervade each species' repertoire. Or can they evolve independently of one another, because each is produced in a different way? If different calls of a species can evolve more-or-less independently, then some kinds probably evolve quickly (e.g. sexual calls), and others slowly (e.g. general-purpose alarm calls), a pattern that will be evident by examining vocalizations in the context of the group's phylogeny ("family tree"). The last part of the puzzle is the vocal organ (syrinx), which will be dissected from museum specimens, and viewed alongside acoustic displays, to give a broad picture of how instinctive sounds and sound production evolve in birds.