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Birds don’t molt all their feathers at once. That would leave them naked, vulnerable and unable to fly. A complete molt might extend over several weeks or months. It progresses with one small section of feathers at a time beginning on the head, face and throat and then moving backward to the tail.

Feather loss is usually symmetrical on both sides of the body. If feathers are lost on the right side of the bird, the same feathers on the left side are lost. This keeps the bird balanced.

You can often observe this symmetry by watching soaring hawks. If you notice a gap (a missing flight feather) on the right wing, there will be a corresponding gap on the left wing. This balance allows the bird to fly reasonable well despite missing feathers.

Waterbirds are an exception to the gradual molt rule. Mallards, for example, molt all their flight feathers simultaneously, usually in mid to late summer after breeding season. Without flight feathers they can’t fly and are vulnerable to predators so they spend countless hours floating in the center of a pond where they are reasonable safe from land-based predator. This is where the term “Sitting Ducks” is said to have originated.

You may have noticed that you do not see many male Mallards at this time. That’s because they go through a quick molt and change into what is called their “eclipse plumage.” Males lose their glossy green head feathers and look more like female Mallards. So at that time, you will see lots of “females” and no males. In early fall another molt brings back the classic male green head for the male Mallard.