More on birds, language and non-human primates.
Regarding cuckoos, I don't think any research has been done on them specifically. The best book on this general topic is Bolhuis & Everaert's "Birdsong, Speech and Language. Exploring the Evolution of Mind and Brain (2013, MIT Press). A bit old, to be sure, but still the most recent synthesis out there. Another important point about bird song and human language - not all birds sing. It's mostly the passeriformes or perching birds and there generally only the males sing. Song is used to attract mates and defend territories. Very interestingly, most species studied show lateralization effects with the left side of the bird's brain being in control of song production. This is somewhat similar to lateralization of language function in human brains.
As to language in non-human primates, I don't think there is any real evidence that any non-human species uses language, even when they are taught sign language. A great deal of that research demonstrated the Clever Hans effect more than anything else, along with wishful thinking. Which are sort of the same thing I guess. Boles in his "Cognitive Evolution" (2019, Routledge) concludes that non-human primates do have a sort of small "vocabulary" of signs and can use these. But this is far from a real language, in the sense that human language (whether spoken or signed) is both productive and referential. Nor do non-human primates have the neruoanatomical connections that support human language, although chimps have sort of the precursors as shown by Rilling et al. (Nature, Neuroscience 2008, 11, 426-428.
OK, I'll shut up now as this may be more than anyone wanted to know.
Regarding cuckoos, I don't think any research has been done on them specifically. The best book on this general topic is Bolhuis & Everaert's "Birdsong, Speech and Language. Exploring the Evolution of Mind and Brain (2013, MIT Press). A bit old, to be sure, but still the most recent synthesis out there. Another important point about bird song and human language - not all birds sing. It's mostly the passeriformes or perching birds and there generally only the males sing. Song is used to attract mates and defend territories. Very interestingly, most species studied show lateralization effects with the left side of the bird's brain being in control of song production. This is somewhat similar to lateralization of language function in human brains.
As to language in non-human primates, I don't think there is any real evidence that any non-human species uses language, even when they are taught sign language. A great deal of that research demonstrated the Clever Hans effect more than anything else, along with wishful thinking. Which are sort of the same thing I guess. Boles in his "Cognitive Evolution" (2019, Routledge) concludes that non-human primates do have a sort of small "vocabulary" of signs and can use these. But this is far from a real language, in the sense that human language (whether spoken or signed) is both productive and referential. Nor do non-human primates have the neruoanatomical connections that support human language, although chimps have sort of the precursors as shown by Rilling et al. (Nature, Neuroscience 2008, 11, 426-428.
OK, I'll shut up now as this may be more than anyone wanted to know.