Duckling pecking at gosling

[GooseMoatGuard]

We have a couple of ducklings and goslings in the same brooder. All of them are about 1.5 weeks old. Two of the ducklings just started pecking at the goslings' lower back. It doesn't seem to hurt and the goslings ignore it, but it does cause their lower back to be constantly "wet" (not drenched but just as if something was nibbling on it...). Any idea why they are doing this and if it's a problem/how to stop it. Only 2 ducklings seem to be behaving this way, the others get along perfectly.

 

[sourland]

How much space do they have. This behavior frequently starts when they are overcrowded and become bored.

 

[GooseMoatGuard]

It's getting a bit small indeed. But we are selling some of them today and looking for a bigger space so hopefully that fixes it. Thx