Strange behavior from Mallard hen

[Zombified]

For roughly a week now, my Mallard hen, Pyrrhos, has been disappearing during the day, and returning later in the night. Her schedule has changed a little. She's gone more in the evenings. We don't go to bed ourselves until we see her, but I don't know if she stays all night, or if she disappears periodically throughout the night. I believe that she's sitting on eggs, as before, she was giving us about one egg every three days, and I haven't found one egg from her for about a week and a half.

She came back today while I was in the middle of photographing the other ducks (around 11am) so I was able to video tape the even stranger (to me, a duck noob) behavior that she exhibits when she does come back. The "strange" behavior is more in the beginning of the video. She seems puffed up, and is quacking like she is in the video. That's been going on for about thirty minutes. My dad suggested that her physical appearance (sort of "squished" looking) could be due to the fact that she's hiding under our shed, which is very low to the ground, and barely big enough for her to fit under.

Not sure if it's related, but our drake also follows her around very closely when she does re-appear.

Anyways, here's the video. I hope it's nothing serious, and you guys can help me out in understanding what this is.

 

[Amiga]

She's acting broody. She is quite vulnerable to predators if she is just wandering off at night, sitting on those eggs.

I would get her to a safe place a.s.a.p.

 

[Zombified]

We can't really move her or get to her at all under the shed. She herself can barely fit through, haha. We also don't have a huge predator problem. Most critters stay away from our yard because of my dog, who is not only protective of everyone in his family, he will kill anything that isn't family that goes into our yard. Thankfully, he views the ducks as family.