We find the odd one on the runway with no strike report. Some with obvious collision damage others that have been hit by vortex. The pilots obviously oblivious to the fact they had a strike.
Any bird that gets hit above 100kts is going to be well broken up and only recognizeable as a blob of feathers.
Birds found on the runway mostly intact were the one killed by the aircraft wake.
The occasional dead bird on the runway is very unlikely to be the one associated with your aircraft strike and a waste of time to report it as such.
Bird goo stuck to the aircraft or engines is far more convincing.