Go to the redwood, look at the trees they'll often fly from one tree to the next. It can take some time to find but when you do they spawn in bunches. Now here's a nifty trick. Not all "grab point" on tree work perfectly, if the archa can't grab the tree it'll just fall vertically to the ground for not only an easy time to tranq it, but also other archas might fall to the ground near the same spot when they come along to feed! I tamed 3 archa in one spot for the price of one (fourth one got away).
Careful about the wildlife especially the angry birds