Worked out what I was doing wrong with Tyto alba.
What I'd done was to confuse the standing position with the perching position.
I had my poor Tyto impossibly standing on a log.
The perching position, of course, involves the bird bending its leg-joint (knee?) backwards.
Took a lot of paint to correct this.
But now it at least looks semi-correct.

I shall probably qualify for Mr Ornithological Stupid 2008.

Sledge