As fooot points out, we do have a few questions that are about birds as aviators. Even though it's only 16% of the questions in the tag, I'd prefer to avoid mistagging those with bird-strike. One complication is that a few of the bird-strike questions are only indirectly about strikes: they're about bird control at airports or other related issues.
I'd be in favour of creating a new tag for the birds-as-aviators questions, maybe bird-flight or natural-flight to include things like bats too.
If we do that, we just have to decide what to do with birds. Either we should remove it completely (and re-tag all existing questions to one of the two more specific tags), or make it a synonym of one of the more specific tags. Although it makes less sense as a logical classification, I'd propose making it a synonym of bird-strike, for two reasons. First, only a small number of existing questions would have to be changed. Second, since most questions are about bird-strikes, and people tend to choose the shortest, most obvious tag, it makes sense for the short synonym to be for the most common tag: this will result in fewer mistagged questions going forward.