I highly doubt any flying birds will find them in the grass. Only things would be Wild cats I guess. I don't know if anyone on gum tree will buy them.
A flying bird may not see them but then Hawks have incredible eyesight. However, a bird sitting in a tree will most likely spot them. Hawks do not just attack when flying and have been known to jump down from a branch and pick off prey.
Just a thought but you could try posting your question in the Aussie thread https://www.backyardchickens.com/t/...-that-funny-little-island/31430#post_17715947 where I know there are some people who keep quail and they may also be able to answer the question if anyone would buy them.