This is not ethical and is a…

This is not ethical and is a huge waste. Shooting nesting birds at any time is unacceptable but to leave them to do nothing but rot is wasteful. Don't condemn babies to slowly starve to death all for human interest.
There is not enough verifiable scientific evidence that these birds are solely responsible for the fish decline. If anything we need to take a look at human activity in the area to rectify the problem and how we can help the ecosystem heal.
We can find a different solution if we try, we don't need to always resort to killing the predator and think it will solve our problems. History has shown it doesn't work as every ecosystem needs checks and balances that mother nature will take care of if we just allow it.