Pond looks like it's always been there. Are the ducks using the island?
I put an island on my first pond so the ducks would have a safe place. The never use it. Instead, they like to sleep on the side of the pond, farthest away from the house, and where the coyotes can get them easier. I had to put up an electric fence to keep the coyotes out!!!
They use it quite a bit. I used the duck house for the white ducks when they were little and still in an enclosure so they know it. There is only 1 of the 4 white ducks left (Maveric), sad day. When I got the mallards (Rooster and Phoenix) they were a little bit older and did not need a light. So I built their enclosure about where the white duck is hanging out in the picture above, when it was still just a little pond. I put the fence half on the dry land and half in the water. So the OG ducks have history in the location that is now the island. That's probably why they use it. You can tell they feel safer on it.
They still sleep on the side of the pond some too.