Loyalty to dead mate

Two days ago, driving home, I passed a Mallard drake standing very near the road, beside what appeared to be a hen. I stopped to check. Indeed, the bird curled on the ground was a cold, stiff Mallard hen. I assumed she had been hit by a car, tossed or moving to the boulevard and dying there. The drake flew at my approach. One day later, a grandson and his mother drove past that spot. The body of the hen remained, the drake again standing nearby. Later that same day, I drove by. The hen was gone, but the drake Mallard continued to stand on the spot of the hen's death, well more than 24 hours after her death.