Flight feather

Flight feathers are special long, stiff feathers that help birds fly. They are found on a bird's wings and tail. The ones on the wings are called remiges, and the ones on the tail are called rectrices. These feathers help birds fly by creating thrust and lift.

Some birds use their flight feathers for other things, like showing off to find a mate or making sounds. For example, owls have tiny bumps on their wing feathers that help them fly quietly. Woodpeckers have very stiff tail feathers that help them stay steady while they peck at trees.

Even birds that cannot fly, like ostriches, still have flight feathers, though they might look different from the feathers of flying birds. Losing these feathers can be a problem for birds because they might not be able to fly until they grow new ones. Different birds have different ways of dealing with this.

owls woodpeckers pennaceous feathers wings thrust lift flight

Remiges

Remiges are feathers on the back side of a bird's wing. They help the bird fly by giving it push and lift. These feathers are stuck tightly to the wing bones by ligaments and strong tissue. Remiges on both wings are usually the same size and shape, unless they are damaged or changed by mutation.

Primaries are the longest and narrowest remiges, attached to the bird's "hand." They are very important for flapping flight, helping the bird move forward. Most of the push in flight comes from these feathers when the bird moves its wings down. Secondaries are attached to the bird's forearm and help shape the wing for lift. They are shorter and broader than primaries. Tertials are shorter feathers that protect the folded primaries and secondaries. Tectrices, or covert feathers, protect the flight feathers from harm. Some large birds have special narrow parts on their outermost feathers to help create more lift when they fly. Feathers on the alula, or "bastard wing," help birds fly slowly without stopping. Young hoatzins have slower feather growth on their wings because they have claws on their first two fingers to help them climb trees.

Rectrices

Rectrices help birds slow down and steer while flying. These feathers are found in a single row at the back of a bird's tail. Only the middle pair of rectrices are connected to the tail bones; the others are held in special areas around the bones. Most birds have six pairs of these feathers, but some birds, like penguins, have fewer, and others, like grouse, may have more than twelve. The number can even vary between individual birds in certain species. Domestic pigeons have a variable number of rectrices due to centuries of selective breeding.

Numbering conventions

Scientists who study birds, called ornithologists, give numbers to the long feathers on a bird's wings and tail. These feathers help birds fly and are called flight feathers.

Feathers on the wing are called primaries and secondaries. Primaries are numbered in different ways, depending on the bird. Secondaries are always numbered from the outside in. Feathers on the tail, called rectrices, are numbered from the center out to both sides.

Specialized flight feathers

Some birds use their flight feathers in special ways beyond just flying. For example, certain birds make sounds with their feathers during flights to show off or claim their space. Male broad-tailed hummingbirds create a high-pitched trill with their outer wing feathers during courtship. The northern lapwing makes a humming sound with its outer wing feathers when showing off. Male club-winged manakins rub special feathers together to make a clear trilling call. Wilson's and common snipe make rising and falling notes with their tail feathers during display flights.

Birds also use their flight feathers to look impressive. Male standard-winged and pennant-winged nightjars have very long or specially shaped wing feathers they show off during courtship. Many male birds, like the ring-necked pheasant and lyrebirds, have long tail feathers they display to attract mates. The birds of paradise have amazingly modified feathers, from very long plumes to coiled ones. Owls have specially shaped wing feathers that help them fly silently while hunting. The tail feathers of woodpeckers are short and stiff to help them climb tree trunks, and some other climbing birds have similar feathers. Scientists are still learning about all the special uses of flight feathers.

Vestigiality in flightless birds

Some birds have lost the ability to fly over time. For example, the steamer ducks still have normal flight feathers, while others like the Titicaca grebe and some flightless rails have fewer primary feathers.

Birds like emus and cassowaries have softer, smaller flight feathers that are not suited for flying. Penguins cover their wings and tails with small, stiff feathers instead of special flight feathers. The kākāpō, the only flightless parrot in the world, has shorter, rounder flight feathers different from flying parrots.

Moult

Birds replace their feathers in a process called moult, or molt in the United States. Feathers stop growing and become worn, so birds need to replace them.

Losing flight feathers can make it hard for birds to fly, find food, or show off during courtship. The timing and way feathers are replaced depends on the type of bird.

Most birds start replacing feathers from a specific spot on their wings or tail and continue in one direction. For example, many small birds begin by dropping two feathers close together and then replace others in order. Some birds, like those living in the Arctic, lose many feathers at once before migrating, while others take longer to replace their feathers. Large birds with short wings often lose all their flight feathers at the same time, making them unable to fly for a few weeks but keeping them safe from predators for a shorter time overall. Different birds have unique ways of replacing their feathers to suit their needs.

Age differences in flight feathers

Young birds and grown-up birds have different kinds of flight feathers. When baby birds grow their first feathers, they all grow at the same time. These first feathers are softer and not as strong as the feathers grown-up birds have. Grown-up birds replace their feathers slowly over many years. Because of this, young birds' feathers wear out faster.

You can often tell the age of a bird by looking closely at its feathers. As feathers grow, they can show light and dark bands, like tree rings. These bands can tell us about the bird's daily food and health when the feather was growing. Young birds' feathers are usually narrower and have sharper points than grown-up birds' feathers. This can make the edge of a young bird's wing look jagged when it flies, while grown-up birds' wings look smoother. Young birds may also have longer tail feathers or shorter wing feathers than grown-up birds, depending on the kind of bird they are. This helps them learn to fly better even though they are still learning.

Wing formula

A wing formula helps us understand the shape of a bird's wing using simple math. It is useful for telling apart birds that look similar.

To find a bird's wing formula, we measure the distance between the tip of the longest wing feather and the tip of the feather that covers it. Sometimes this distance is a positive number. This means the longest feather sticks out past the covering feather. Other times it is a negative number. This means the longest feather is hidden under the covering feather.

We also measure the differences in length between the longest wing feather and all the other wing feathers. If any feather has a notch or a small cut along its edge, we note how deep that notch is. All these measurements are taken with the bird's wing closed so the feathers stay in their natural positions. Birds of the same species can have slightly different wing formulas, but closely related species usually have clear differences in theirs.

Primary extension

The primary extension shows how far a bird's longest wing feathers stick out past the next set of feathers when its wings are folded. This helps us tell apart birds that look similar. For example, the dusky flycatcher has shorter extensions than the Hammond's flycatcher, even though they look alike. Some birds, like Europe's common skylark, have long extensions, while others, like the Oriental skylark, have very short ones.

Birds that fly long distances during migration often have longer primary extensions than birds that stay closer to home.