Here are some reasons why I would not reccomend taming a Terror Bird:

-Extremely difficult to knock out (They are always in groups and run very fast)

-Torpor runs out very quickly and for a 10+ level one, you will need 100 or more narcotics

-Once tamed, they have terrible stamina, weight, and health

The only two upsides of taming a Terror Bird is that they are fast, do a decent amount of damage, and the fact that they can glide.

If you looking for a pack animal, this is the best creature for that (besides dimporphs).

But if you are looking for something that can be useful on its own, I would not tame these.