Often a birdhit doesn't really damage the helicopter as it does the bird. Engine problems would be very unlikely for a helicopter. Rotor problems unlikely as well. Maybe a broken windshield or a dent, anything worse than that means you must have a REALLY unlucky day.

My experience comes from civil aviation, 99.9% airplanes. Where, with all sizes of airplanes, birdhits are an issue. The damages can be quite severe both to fuselage and engine.

Agreed, it would be really unlucky. Yet, incidents occur frequently especially near airports and very often this results in the airplane returning to the airport to make sure no damage occurred.

FAA animation: http://youtu.be/imDFSnklB0k (granted a flock of birds, but resulting total engine failure on BOTH engines)

I suppose it would be rather easy to have a difficulty setting turn on/off bird collision depending on your gameplay. I don't see it would be that difficult for BI to implement =)

edit: Found this one about a helicopter, http://youtu.be/98wSezE7WJY. Again, not saying it should be very common, but every now and then it could be a possibility. Would also make interesting scenarios.

There's ofcourse a big difference between civil and military aviation. If a military aircraft is on an important mission, it will most likely choose to continue it's mission. During peacetime it should RTB and inspect for damage. I've had a couple of birdhits in real life and never had much more than blood, guts and feathers on the aircraft. I have to admit, I've never hit a really big bird though. But, like I said, if the mission's important, you continue with the mission. That's what game players will also do. Unless you make it so that birds will always cause severe damage which makes continuing the mission risky or impossible. This, however, would not be realistic.
Most (military) helicopters have filters in front of the engines, so birds aren't likely to cause a flameout on helicopters. Also, it's easier for a helicopter to dodge birds.

The potential to weaponize seagull spectator mode is too good to pass this up!

We are very sorry, this issue was closed as no-bug. In Arma seagulls will be always deafeated by helicopter rotors. Maybe in future there will be more dangerous holo-seagulls. :)