less than 25% of actual birdstrikes get reported. Presumably because the crew does not know for sure. however the bird does know and leaves its imprint to be seen on the engine, airplane, or runway.
Even when it's suspected as a might-of, the crews have been hesitant to write a maybe in the log without supporting overt evidence.(it takes time to write up a log when you could be off the plane heading to another gig)
I tend to think that the so called "new" reporting requirements mentioned above might only apply when the crew logs actually reflect the word bird or animal