" For northern species they have Black Walnut, Black Cherry, Hard Maple, White Ash, White Oak (Red Oak is included in these piles), European Beech, French Oak and Sapele Mahogany. They also have a bunch of exotic hardwoods from South America like Kwila, Purple Heart, Green Heart, Tonka and various Gums from Australia."
Good to know.All those woods in the first sentence will make good bows(though I don't know about Sapele,may not be up to the task.
Never tried kwila for a bow, but I wouldn't be surprised if it made a good bow, as its hard and heavy. Surprisingly I haven't heard of anyone trying it for bows either.
Purple heart can make good bows providing they are long enough and wide enough, otherwise you risk chrysalling , and explosive tension breaks.
Add a bamboo backing to many of the South American exotics and you can get good bows. Do you have any bamboo suppliers or local groves that you could trim?
Not a fan of most Aussie gum trees for bows. Some will make good bows, other pieces from the same species will chrysal despite wide shallow limbs and good tiller. They just aren't as predictable as Northern hemisphere timbers. Stats look good on paper, but usually don't translate to good bow wood, in practice.
Gathering Black Maire sounds like an interesting adventure. If they don't grow too large in diameter, and if it splits well with wedges you could probably pack some out, especially if you have a friend. Work off the excess bulk, into a blank. Nevertheless it will be hard work(I used to do quite a bit with wild grown osage, and native timbers here in Australia). The older I get the less attractive the idea becomes.