Clearly there was a termite issue in this header previously. Thankfully, it's WAY oversized for this small window so there's still enough structural integrity to carry the load. Getting drywall screws to hold is another matter so I used a 3" screw to do some testing. Looks like if I use at least 2-1/2" screws I'll get enough "bite" to keep the greenboard in place. First, I need to vacuum up all the termite poop...