[capt. norm]

Birds dying from flu would probably fall off their perch or die on the ground individually.

For a large number of birds to die all at once it would have to be some kind of quick-acting airborne gas/vapor that killed them.

It's the timing that gives it away.

[Sender]

True, avian flu would not cause a flock to fall out of the sky. Sounds like noxious fumes. Probably just the smokestack from the Happy Meal toy factory.