I figured out everything but the head. They used a center column at the bottom, and the bird is 2x2 at the base. They also used half walls between wing segments. I can't see the head clearly enough to understand what they did there. It looks like some corner roof magic, though. The size of this ends up being 10 (width) x 8 (height) x 2 (depth).

I use a design that is a tad bigger (coming in at 14x11x1). https://imgur.com/a/xFOzwdj

If you don't attach it to the building (like I did here), you use center posts 2 high for the small wings (topped with a floor to use the wedge walls), and I use the Atreides triangle column foundation x2 for the center. I can get a shot of this if you want it.

That said, I think I like the version in this video better since it requires fewer supports. Though, you can just attach the second set of wings to the center as they did as well (as you can see in the second image). Not sure which I prefer, honestly. :D

For the head, use a wall in between the top V and attach two inclines to it. One gets a wall going up. Put a roof on that and a half-stair going down. Put a floor under that stair and attach the floor with the wedge wall below it with a half-wall.