mallard eggs

[Nana of the ducks]

I am worried. long story but would like some help. I have a pet female mallard. She is almost a year old. she started laying eggs and i decided to let her hatch one since I live in a development. she has been sitting on the egg.
Here is where the story changes. My sister had a female mallard laying on 9 eggs. The female was killed by a fox. All the eggs were fertile. I candled my female's eggs which showed it was not fertile, so I exchanged her egg for one of the fertile ones. She is sitting on it. The problem is since the mother that got killed was wild, we are not sure how long she had been sitting.
Sophie (my duck) is still sitting on the egg. The egg was initially a cream color. When she left the nest, this am I checked the egg. It was showing an air sack and mostly dark the rest of the egg. what concerns me is now it is a blueish color. I did not detect any odor.
Can someone please help me? It breaks my heart to see her sitting on an egg that is not to hatch.
HELP

 

[nchls school]

Eggs will appear to change colors slightly as they become more opaque with the developing embryo so if the egg does not appear blotchy looking it is likely fine. You could post a picture of the egg being candle from the side and we'd be able to tell you. If you do this do not candle from the end, but from the side so the air cell shows clearly.

 

[Nana of the ducks]

I am worried. long story but would like some help. I have a pet female mallard. She is almost a year old. she started laying eggs and i decided to let her hatch one since I live in a development. she has been sitting on the egg.
Here is where the story changes. My sister had a female mallard laying on 9 eggs. The female was killed by a fox. All the eggs were fertile. I candled my female's eggs which showed it was not fertile, so I exchanged her egg for one of the fertile ones. She is sitting on it. The problem is since the mother that got killed was wild, we are not sure how long she had been sitting.
Sophie (my duck) is still sitting on the egg. The egg was initially a cream color. When she left the nest, this am I checked the egg. It was showing an air sack and mostly dark the rest of the egg. what concerns me is now it is a blueish color. I did not detect any odor.
Can someone please help me? It breaks my heart to see her sitting on an egg that is not to hatch.
HELP

Thank you. Will get a pic when she comes out again

 

[nchls school]

Thank you. Will get a pic when she comes out again

You're welcome.

 

[nchls school]

Thank you. Will get a pic when she comes out again

You're welcome.

 

[Nana of the ducks]

She came out. Egg was not good. Bad smell. Should I put another egg in there that another duck laid, (?) Fertile. Or just put none in

 

[nchls school]

She came out. Egg was not good. Bad smell. Should I put another egg in there that another duck laid, (?) Fertile. Or just put none in

If you can get another egg that is fairly developed like the one she had, if it had lived, yes, if you want to. Otherwise it would be better for the duck just to remove the egg and nest. Brooding takes a toll on a bird's body and too long on the nest is not healthy.