Just to update where I am at. The left hand bird is complete, background all done. I set the smaller tesserae all swirly around the tail feathers to accentuate the movement of them . Then using larger squares in straighter lines to strengthen the shape of the head and neck.
I think it seems to work well, but grouting it may change that! I am currently working on the other sides background which is filling in much quicker.
The birds heads and bodies are made of teal, and two shades of blue (slightly tealish tones), some glass beads thrown in for variety. The wing feathers are a variety of crockery and the tail feathers are just porcelain mosaic tiles cut up. I am really pleased with them.