Runner duck help please

[goldfishcracker]

I have 4 runner ducks, theyre 2 months old and one of them (we think is female) has been occasionally quacking really loudly in a row then being quiet, kind of like shes calling? She has access to food, water and shelter so i dont know what it could be.. im scared theres something wrong with her but shes walking, eating and drinking fine..

 

[chickens really]

Hens love to quack....Mine quack lots....When they see me, snack time, feeding time, when I fill the pool they QUACK...
Sounds like she has found her voice...I'm sure she is fine...