The discussion is more heated than I wanted. I do not felt really offended in the discussion, and I understand that some explanation is often necessary in a lot of situations.
Again go back to the question. I really think that sometimes there are good reasons to doubt a book. The case with Asian and Japanese Paradise Flycatcher is particular difficult. I think the best reference book is Robson's "Bird of South-east asia". The key id features are:
1. Glossy blue crown points to Asian
2. Colour contrast between throat and breast (or between crown and face in the illustration) points to Asian
3. The sharp change of the colour from the breast to the belly points to Japanese
4. Brownish tinted breast points to Japanese
5. Pale bill points to immature or 1st year
I believe the similarity and difference between Asian and 1st year Japanese is not well discussed in the reference books. I think 1st year Japanese is very similar to the Asian. I have the following comment and suggestions.
1. The colour of the upperparts (back and tail) is not a good feature at all for 1st year Japanese. The colour is surprisingly difficulty to separate in the field and also in photo, due to the highly varying light conditions.
2. The glossy blue on crown seem to be convincing for Asian.
3. Tbe contrast of the throat to breast does point to Asian, even for the supspecies that we have in HK. However, a few Japanese can show very similar constrast. So this feature is not safe. However, I think any brownish on the breast definitely points to Japanese.
4. Robson's illustration for Asian is good for wintering Asian, when the birds have new crown feathers and warn feathers on the rest of the head.
5. I have a lot of doubt on using pale bill/bill-base as a feathers for 1st year Asian or Japanese.
After all, I believe that the bird in hand is an Asian Paradise Flycatcher, and it could be an adult female.
HF Cheung
