Train tracks? Early Disney? That means a cow must be blocking the way. That eventually happens in “Mickey’s Choo Choo” (1929), along with some other re-used ideas, but first we have a cartload of ducks stuck on the tracks.
Here comes Mickey’s Choo Choo.
And when the feathers clear...
You can see the ducks are into the same quacking cycle animation. Compare their heads in the above drawing with the first one posted.
Ub Iwerks gets the only credit. Trésors Disney says Ben Sharpsteen animated some scenes, too.