Compare and contrast the mating signals of two very different vertebrate orders: anurans (frogs and toads) and passerines (songbirds). What features do the anuran and passerine mating vocalizations share in common? What features are different? Discuss the mating signals themselves (acoustic structure, including elements and complexity), as well as how (anatomy and physiology) and why(sociology) those particular vocalizations are produced (by speaker) and preferred (by listener). This discussion should include comparison of the physical and social environments in which frogs and songbirds live and what kinds of socio-ecological problems each is required to solve. Your analysis should address at least two of Tinbergens four perspectives on animal behavior: adaptation, mechanism, ontogeny, and phylogeny.