Part of the space between the firmament and Earth is the area in contact with the Earth that we call the atmosphere, or sky. This is where the birds fly. It's referred to as the open firmament.
"First lemurs; some modern groups of birds". Modern is a concept in the evolution narrative. The Paleocene is recent, therefore according to the narrative anything different about it can be called modern. It's meaningless.
"Rise of higher insects and birds" is an example of Paleodoublespeak. Jurassic sediment contains the preserved remains of dead insects and birds. That's not evidence of their rise. It's evidence of their extinction.
As we continue down our rabbit hole into the confluence of gravitation and redemption it's going to be helpful to think in terms of gravity, weight and weightlessness. The word redeem has some meaning to this effect.
Knowing the preferred habitat of dragons and owls will help us to answer the question: if humans and dinosaurs were alive on the earth at the same time, why don't we find their remains preserved together?
Seraphim and Cherubim were created in the firmasphere on the 4th day. God recombined their characteristics as he created the moving creatures in the hydrosphere and fowls in the atmosphere on the 5th day.
Bats are birds is an excuse that some people use to reject the Bible. It requires using the words "bird" and "fowl" as synonyms, and the misapplication of phylogenetic systematics to a spherogenetic creation.
If you want to believe that earth is flat no one's going to stop you. However nothing in the Bible, either in the meaning of words or in the context of passages, requires you to believe that earth is flat and has an edge.
The biological definition of life and what the Bible describes as living aren't the same thing. This is important to know as we see how the process of creation unfolded. Biology is the foundation of secular humanism.