One of the interesting parts of the owl is its flyby ability
Flyby: The owl doesn't provoke Opportunity Attacks when it flies out of an enemy's reach.
With this ability, could a druid wildshape into an owl (lets assume circle of the moon bonus action transformation for the sake of action economy) and go for a direct attack against the eyes, blinding the enemy? And if so, what's stopping the druid from abusing this ability and making every enemy they face blind with no opportunity attacks?
Considering how crippling a permanent blind condition is…
A blinded creature can’t see and automatically fails any ability check that requires sight.
Attack rolls against the creature have advantage, and the creature’s Attack rolls have disadvantage.
This just seems like a really powerful strategy and I can't see any downsides to just spamming this strategy, are there any drawn backs I'm not seeing (pardon the pun)? Or are owls just straight up unable to be that specific with there attacks?
To be specific, this question is not called-shots or "could that attack work?", but rather preventing abuse of the ability or "what is the counter towards the attack?" Without an attack of opportunity I don't see how a creature could prevent this from happen or counter the attack with an attack of its own, it just seems like a free blind condition on anyone you chose with no consequences.
Best Answer
I'm going to address only the "flyby abuse" aspect, because Aiming at specific body parts I think covers the issue of "called shots" pretty well.
There is, however, an easy counter, which I've used as a DM on a player who was convinced that the owl familiar meant a free, unstoppable "help" action each turn (despite my repeated warning that that familiars that engage in combat are fair game for enemy attacks): flyby attack does not protect against readied actions. Any even slightly intelligent enemy faced with a repeatedly swooping owl will not hope for opportunity attacks but instead ready to swat it from the sky. Poor beastie has AC 11 and 1 (one) hit point. Problem definitely countered.
It's worth noting that with that AC and the single hit point, the owl is a very vulnerable target in combat to any ranged attacks, as well. Even if the intended victim's entire party has no ranged attacks, an improvised weapon attack like throwing a stone is quite likely to bring it down.
Of course, you make the problem worse if you allow called shots targeting vulnerable areas. If you really want to to house rule that, I encourage you to make the chance of success low enough that this remains a very risky tactic.
Also, in the case of a wild-shaped druid, the consequences can be more dire than those of losing a familiar and having to re-cast that spell, since losing single HP means the druid is:
Probably going to take some amount of excess damage — if the retaliatory strike does 20 damage, that's 19 left over in "real" damage for the druid's native form. Compare instead being a giant snapping turtle: 75 HP.
And, in taking that damage, the druid is back in native form. That in itself may be inconvenient — you might find yourself in melee when you didn't want to be! — but worse, there's no "you drift gently to the ground" protection for this situation. You are going to be prone, and may take additional bludgeoning damage from falling.