I got very sick last week, and since I had no energy for doing much, spent some time going through some of the blogs linked to this site.
As I was scrolling through Adolph Khor's site, I came across some interesting minivet photos he'd taken at Ulu Muda last November (see this post). The upper two of these photos looked very like a Swinhoe's Minivet, a species not previously known from Malaysia!
Then another bird came to light, this time, on the Malaysia Bird Photography Forum here (you'll need to register to see these), photographed by C V Cheah. More investigation revealed that both birds were snapped at the same spot at the same time, and were part of a flock (at least some of which were Ashy Minivets).
Differences from Ashy are subtle, and I'm still looking into the range of variation shown by both species.
But it strikes me that it would be a worthwhile exercise for birders and bird photographers to pay close attention to Ashy Minivet flocks, especially in the north of the Peninsula. Here's a brief guide to the differences between non-males.
Wing pattern is not very much help, since there seems to be much variation, especially among worn birds. However, when fresh, Swinhoe's sometimes shows a neat pale yellow or buff bar on the greater coverts which Ashy appears not to show. Calls are also very similar. I've highlighted the four main things to look for on females/1st years, and would stress that it's probably necessary to get at least three out of four of these to be confident of identification.
Here they are side by side for easy comparison.
I'll add the males when I have a bit more time... or get sick again (hopefully the former!). I'll also add a bit on Rosy Minivet, a similar species in both plumage, vocalizations and rarity.
My main sources of photos for learning about Swinhoe's Minivet are:
1. Oriental Bird Images
2. The Hong Kong Bird Watching Society website (minivet section)