Time to get my ducks in a row....

The most popular theory suggests that "ducks in a row" came from the world of sports, specifically bowling. Early bowling pins were often shorter and thicker than modern pins, which lead to the nickname ducks. Before the advent of automatic resetting machines, these "duck pins" would be manually put back into place between bowling rounds. Therefore, having one's ducks in a row would be a metaphor for having all of the bowling pins organized and properly placed before sending the next ball down the lane. Many bowling alleys still offer "duck pin" lanes with smaller bowling balls and shorter pins.

Another theory comes from the world of nature. Mother ducks often corral their young offspring into manageable straight lines before traveling over land or water. Any stragglers or escapees would be noticed as long as the integrity of this line is maintained. The idea of getting all of one's ideas or ingredients or team members in one organized line would be similar to a mother duck getting all of her literal ducks in a row. One concern with this theory is the use of the word ducks, since baby ducks are more correctly identified as ducklings or even chicks. The common expression suggests adult ducks, not necessarily younger ducklings.

There are also sources which argue the "ducks in a row" element refers to a carnival game or two. One popular carnival game involves the player using a small caliber rifle or air gun to knock down moving targets. Quite often these targets are in the shape of ducks, and a conveyor belt system makes sure the duck targets are aligned in a consistent row. It is possible that the expression came from the benefit of having all of the targets (ducks) arrive in a predictable and organized order.