We did activities from Letter D for Ducks printables.finger puppets to do "Five Little Ducks" which can also be a finger play, song, and we have a book with the words as well.
Five Little Ducks (that can go with the finger play), Little Quack, and the classic book Make Way for Ducklings.
Zoobooks at one time and they had an edition with Ducks so we looked through that book. I read a few things, but mostly my son looked at the pictures.
We also looked at National Geographic for Kids for more facts about ducks.