If u want to avoid long wait times between feeding I suggest trapping the Tropeognathus and then using 1 or 2 regular (not chain) bolas to drop its hunger level as doing this seems to make it lose hunger very fast. Then when u want to tame it place your balista, fire a chain bola at it, pick up the balista again (for future use) and then run up from behind the bolad Tropeognathus and feed it.

More Tropeognathus Taming & KO Tips