Ducks are widely recognized for their ability to take flight, a characteristic that allows many species to undertake extensive migrations. However, the term “flightless” refers specifically to species that cannot achieve sustained aerial locomotion. This differs from the temporary inability to fly that many ducks experience at certain times in their lives. While most duck species are capable of flight, some have evolved to be permanently grounded, adapting to their environments in unique ways.
Truly Flightless Duck Species
Several duck species are flightless. Among the most recognized are the steamer ducks (genus Tachyeres), found in the southern cone of South America. Three of the four known steamer duck species are flightless: the Falkland Steamer Duck (Tachyeres brachypterus), the Chubut Steamer Duck (Tachyeres leucocephalus), and the Fuegian Steamer Duck (Tachyeres pteneres). These ducks are named for their distinctive “steaming” behavior, where they flap their short wings and use their feet to propel themselves rapidly across the water, resembling old paddle steamers.
The Falkland Steamer Duck, endemic to the Falkland Islands, is a large bird that inhabits rocky shorelines. It feeds on marine mollusks and crustaceans by diving or dabbling. The Chubut Steamer Duck is native to a coastal stretch in Argentina and can reach speeds of up to 24 kilometers per hour when steaming to escape predators.
Beyond the steamer ducks, New Zealand’s subantarctic islands host two other flightless species: the Campbell Island Teal (Anas nesiotis) and the Auckland Island Teal (Anas aucklandica). The Campbell Island Teal is a small, dark-brown duck found exclusively in the Campbell Island group, foraging for invertebrates and plant matter in grasslands and wetlands. The Auckland Island Teal, slightly larger, is endemic to the Auckland Islands. It has very short wings, adapting to a semi-marine lifestyle and often feeding in kelp beds.
Domesticated ducks, such as the Pekin, are often flightless due to centuries of selective breeding. They have been bred for traits like increased body size and meat production, resulting in a heavy build and small wings that prevent sustained flight. While wild Muscovy ducks can fly well, their domesticated counterparts often cannot get airborne for long distances.
Why Some Ducks Evolved to Be Flightless
The evolution of flightlessness in ducks is an example of adaptation driven by environmental factors and resource allocation. A primary reason for losing flight is the absence of terrestrial predators in their habitats. On isolated islands, where large predators are scarce, the energy-intensive ability to fly becomes less necessary for survival. This reduced evolutionary pressure allows ducks to adapt to a grounded existence.
Maintaining the structures required for flight, such as large flight muscles and lightweight bones, demands significant energy. When flight is no longer necessary, this energy can be reallocated to other biological functions, like reproduction or growth. Over generations, ducks in predator-free environments may develop physical changes, including shorter wings, smaller pectoral muscles, and denser bones, making flight increasingly difficult or impossible. For example, the Auckland Island Teal has disproportionately small pectoral muscles and reduced wing size.
Domestication also plays a role in the flightlessness of certain duck breeds. Through artificial selection, humans have bred ducks for specific agricultural traits, such as rapid growth and increased body mass for meat production. This breeding often leads to a heavy body with wings too small and muscles too underdeveloped to support flight, as seen in Pekin ducks. While they may retain the instinct to flap their wings, their physical attributes prevent them from becoming airborne.
Temporary Flightlessness in Ducks
Not all ducks that appear unable to fly are truly flightless species; many flying ducks experience periods of temporary flightlessness. The most common reason is the annual molting process, particularly during the “eclipse plumage” period. During this time, ducks shed all their primary and secondary flight feathers simultaneously. This renders them completely flightless for several weeks until new feathers grow in and mature.
This simultaneous feather loss is a strategy some waterfowl employ to replace worn feathers efficiently, but it leaves them vulnerable to predators. To compensate, many duck species seek out secluded areas with abundant food and cover, such as dense vegetation or open water, during their molt. This flightless period typically lasts a few weeks.
Beyond molting, other factors can temporarily prevent a duck from flying. Young ducklings, for instance, are relatively independent shortly after hatching, but they cannot fly. Their flight feathers and muscles need time to develop, with most duck species taking their first flights around 8 to 12 weeks of age. Injury or illness can also temporarily impair a duck’s ability to fly, grounding it until recovery.