From Melvin Laureano Nature & Wildlife
A Great Gray Owl delicately testing the strength of a pine tree’s tip before settling-these large owls often perch high to scan and listen for prey below.
Mountainview County, AB
The world’s largest owl by overall length, the Great Grey is mostly air.
Hollow is somewhat misleading. It’s not like a soda straw or pipe, but it’s lined with lattice like structure. It reminds me of a gluten matrix in bread dough!
While every gram counts to a bird, solid bones bend and flex, while birds’ bones are very rigid to withstand the extreme forces flight puts against their bodies.
I’m curious to read the linked article in the other reply to get more fine details.