Cryptic species in cuckoos?

[Ian Southey]

This fascinating paper https://www.science.org/doi/10.1126/science.adj3210 looks at the coevolution of the bronze cuckoos and their hosts - mainly warblers.

While the adults look similar there is strong selection in the nests so that the cuckoo's nestlings evolve to have chicks that look and sound their host's chicks while their hosts are also under strong pressure to look and sound different. Particular cuckoo lineages specialise on one host and the chicks match that host quite well but transplants to different hosts were not successful. This suggests that the different host lineages in particular cuckoo spercies have become, or are becoming, different species even though the adults can seem similar to each other. It is also suggested that the host species, gerygones and a thornbill, have chicks that look more different to each other than most other small passerines suggesting evolved defences to cuckoos.

This makes me wonder if there are different host lineages of Long-tailed Cuckoos and the Shining Cuckoos on the mainland and the Chathams, with their different hosts, are evolving seperate lineages too.

Ian