Two-Minute Mystery: Who Killed "Nameless"??

I recently adopted a tame peach face lovebird. The lovebird seemed docile, pettable, although it didn't seem to enjoy the petting too much. I called it "Nameless," intending to name it later. I decided it was probably a male bird, and put it in a cage with Io, a lonely female of mine.

Io proceeded to lift her tail and wings, which is a mating posture. In essence, she was saying she'd like to mate with this male. In other words, she was happy to see him.

I left the happy couple alone but returned several times that day to make sure they were getting along. Specifically, I glanced in the cage to see if anyone was cowering, and I glanced at their feet to see that nobody had bitten feet. Everything seemed fine.

The next day, everything again seemed fine until that afternoon. When I checked on the birds, I found that Nameless had checked out -dead. His body was shoved under the food cup, face into the corner of the cage.

Upon examining the body, I found Nameless had been bitten repeatedly in the head, feet, and rump. A portion of the beak had been bitten off. Tail feathers were pulled out. The wounds hadn't bled. I cried "fowl play!" but my husband said he believed the bird died of natural causes. When he explained his reasoning to me, I had to agree.

Why?