Well, I dont understand it, but...

[leoninathan]

here is my duckling from a 43 day incubation by my chook! The other 2 eggs are making moving noises so i guess they'll be here soon! If anyone can explain this long incubation period, pls do!
https://www.backyardchickens.com/web/user.php?action=editpost&id=40155

 

[Camelot Farms]

Are you completely certain of the incubation period? Could the eggs have been slipped in later by another hen?

Or perhaps your coop is in a crop circle?

 

[leoninathan]

well, i put the duck eggs under her myself at the start of august when they started laying so I know for sure it is at least 40 days, unless the frost slowed them down, it looks like only 3 out of the 6 were fertilised

 

[farmin'chick]

I can't see your picture -- but was it a Muscovy? They have a 35 day incubation period, and so it might be understandable.