[computerdork]

Thanks for the explanation on this. Think I partially understand. Birds can distinguish calls on at least two characteristics, by the sound of it and by its function. And the authors have developed experiments to show that birds can do both. Is this correct or did I get on the wrong track?

[pks016]

Yes. Kind of. They showed that birds can do function/meaning of calls (e.g., contact call group) using the meaning not other cues (e.g. duration, acoustic similarity of calls etc.).

[computerdork]

Ah okay, thanks!