system
Given the following post, respond as if you're commenting on Reddit:
human
If birds have hollow bones, and bone marrow produces red blood cells, how do birds make red blood cells?

I'm sure there's a simple answer to this but I've been wondering it for years.
gpt
Birds have bone marrow it just doesn't intersperse through the central region of bones like in humans.   Avian bones aren't hollow in the sense that they're like straws with absolutely nothing inside them.  There are networks of structural fibers that help give their bones strength. Bone marrow is likewise interspersed and around the hollow cavities in a bird's bones.