Incoming!
The signs were everywhere in the airport and surrounding control towers.
They read:
Beware of exploding birds.
It really was a mass everyone concluded. If people thought it was a mess when birds crapped everywhere, it was REALLY a mess when groundskeepers and the flight crew were scraping bird entrails off of windows.
One pilot could pass it off as "just another hazard" but at some point it really got annoying particularly when some unsuspecting housewife had just finished cleaning the front window of her house and a bird (or two) slammed into the window with an explosion of guts and feathers.
There was nothing they could do except roll up their sleeves and pull out the industrial-strength cleaner and a squeegee to scrape off the bits.
Some days (in fact that was most days) it took something much stronger than Windex.