If you accidentally hit a tamed parrot, your tamed wolves will attack it. In contrast, tamed wolves do not attack tamed cats, tamed horses, or other tamed wolves that you accidentally hit.

In 1.13.2, tamed wolves do not attack tamed parrots. In 1.14 and onward, tamed wolves do attack tamed parrots. (Specifically, I've tested this bug in 1.13.2, 1.14, 1.14.4, and 1.15 Prerelease 1.)

This bug existed in the game a couple years ago (see MC-115277) but was fixed. Around that same time, a very similar bug about tamed wolves attacking tamed cats existed in the game but was fixed (see MC-109663). Last March, it was reported that the cat version of this bug had been reintroduced (see MC-145498) and the bug was fixed again. The parrot version of this bug was probably reintroduced at the same time that the cat version was reintroduced, but was not reported until now.