Idea:

1. The fact that the sequences of glyphs in both Thursday and Saturday are ending with the 'splendid bird' perhaps is astronomical in meaning. It might mean 'standing high in the sky' (like in Sunday).

Jupiter and Saturn are never 'hidden' in the manner of Venus, Moon and Mercury.

2. But it seems also possible to explain the bird high up in the sky as an indication of high position in the society. The story about the foreign chief taking possession of the land and being symbolically killed ends in ceremonies when the foreign chief is made part of the society of the island. And this part is the highest position, the king.