It is my understanding that passeriforme communication relies on more than structure. Recurring "forms" or patterns have been observed and recording+playback at

It is my understanding that passeriforme communication relies on more than structure. Recurring "forms" or patterns have been observed and recording+playback attempted. From what I recall a phenomenon that could be described as a "local accent" (modulation of forms or mutation of patterns specific to a region) seemed essential to generate interest from the studied population. Also: syntax! "Japanese great tits (Parus minor) have developed syntactic rules" https://www.nature.com/articles/ncomms10986 https://www.nature.com/articles/ncomms10986