Is it normal for ducks to bury eggs when not broody?

[Moments]

I just found three eggs that my ladies had laid and buried when I changed the straw in their coop. I candled them and there's not growth. The handful I've gotten from them so far were laid on top of the straw and left there (correction, I forgot we collected one this morning that was sitting on top of the straw in the small area where the buried eggs were). They are out and away from their nest all day but at night the ducks tend to alternate sleeping in that little nook that they lay in. I figured it was cause it was small and cozy.

 

[cheezenkwackers]

They often bury eggs. Perfectly normal!

 

[Moments]

They often bury eggs. Perfectly normal!

I figured but this was the first time they've done it. They were very thorough lol

 

[Jenbirdee]

My ducks always bury them if there's deep enough bedding

 

[citymeetscountry]

My ducks always bury them if there's deep enough bedding

Same

 

[Moments]

Same

My ducks always bury them if there's deep enough bedding

Mine were leaving on top of the straw until now. Actually this morning there was one on top of the buried eggs. The buried ones I didn't find till tonight. The straw is pretty much the same throughout the coop but I guess this area is a little more packed instead of being as loose. I read also that the cooler temps could lead to them doing this? Does anyone have ducks that do this without a drake as part of the flock? How long are fertilized eggs viable without a duck sitting on them? Ours have no ducks on them except during the night when it seems to be the go to spot but isn't always occupied thru the night.