Woodpecker in Vietnam

The difference between the Common Flameback and the Greater Flameback:

The difference between the Lesser Yellownape and the Greater Yellownape:

1/ Lesser Yellownape

- Head: with red colors;

- Underparts: Barred with white and gray;

2/ Greater Yellownape

- Head: without red colors;

- Underparts: all gray;

What is difference between the Laced Woodpecker, Grey-headed Woodpecker in Vietnam?

These two woodpeckers are quite similar: gray face, black cap, red front...But the key differences are

1/ Laced Woodpecker (Gecinulus grantia)
Streaked belly.
If having red, then the red covers: front, cap, nape.
Stripes on the edge of the wing are horizontal compared to the body.

2/ Grey-headed Woodpecker (Micropternus brachyurus)
Gray, or whitish or yellowish belly.
If having red color, then the red only covers the front.
Stripes on the edge of the wing are vertical compared to the body.

What is difference between the Pale-headed Woodpecker, Rufous Woodpecker, Bay Woodpecker in Vietnam?

1/ Pale-headed Woodpecker (Gecinulus grantia)
Some with reddish front, the others with light olive-green head, rufous (reddish) wings.

2/ Rufous Woodpecker (Micropternus brachyurus)
Consistent color: either stripes of dark brown and black or rufous (reddish) and black

3/ Bay Woodpecker(Blythipicus pyrrhotis) 
Gray head or light rufous head,

Some with red color on the lower nape,

Dark (and striped) mantle,
Rufous, reddish (and striped with dark color) wings,