This is a really interesting record (and excellent photos too). I don't have references to hand but winter records of Cuculus in Hong Kong are very rare (hardly any?).
What used to be called Oriental Cuckoo is now usually treated as two species: Horsfield's Cuckoo C. horsfieldi which is a long distance migrant breeding in northern China and Russia and Himalayan Cuckoo C. saturatus which breeds in south China.
Judging by the contrast in pattern and length of the tail feathers (note how new feathers are longer and blacker) this would be a hepatic first winter female. It also seems to me to be (relatively small); potentially a candidate for saturatus which is not yet on the Hong Kong list. (saturatus is potentially more likely in winter too as it seems to be a shorter distance migrant than horsfieldi.)
So, this could be the first record of Himalayan Cuckoo for Hong Kong! (there was a singing bird at Tai Mei Tuk a couple of springs ago, but this has not (yet) been accepted.
At this point I would not say categorically that this is saturatus, but please could you submit to the Records Committee as it is certainly worth detailed documentation.
Best regards and well done!
Mike Leven
