What do the initial cell divisions look like in bird embryogenesis?
This is covered well in almost any text that talks of early embryonic development in birds. Basically, the cleavage divisions look roughly symmetrical if you look end-on from the animal pole. But, as mentioned in the question, the process is quite asymmetrical in profile, with the blastoderm being at one end and the huge yolk occupying the other.

The yolk later gets invested by a layer of cells (the splanchnopleure) to form the yolk sac while the blastoderm forms the embryo proper.

You could see this page for more details. (Not just this page, this site in general is an excellent resource for learning embryology.)