This was a grab shot from my home today - the bird was a long way away then flew briefly flew to a nearer tree where I took this shot with my 500mm f4 and stacked TCs. One shot and it flew. From the collar I deduce it is Dark-sided. Per The Avifauna there are few Spring records of this species and mostly in Woodland. I am in a coastal location.
Considering that an influx of Grey-streaked Flycatcher arrived in these 2 weeks, I think you can safely bet Grey-streaked Flycatcher, if you haven't seen white spots on mantle or undefined marks on breast.
Also the length of the wings (wing tip reach 2/3 of the tail) also indicates Grey -streaked Flycatcher. Author: ajohn Time: 2/05/2008 16:21
Note that the white spots on the mantle are a feature of juvenile plumage (in all flycatchers). They are useful because Dark-sided often migrates in juvenile plumage, unlike other species - but even dark-sided should not show these white spots at this time of year.
I agree with Gary, however, that this appears to be Grey-streaked. The colour and structure fit better for this than dark-sided, and it is obviously the commoner species at the moment.
Welcome to HKBWS Forum 香港觀鳥會討論區 (http://hkbws.org.hk/BBS/)