#Alula feather full#

Haecheon Choi, the corresponding author of the paper. The role of the alula in avian flight is just one example.' says Dr.

#Alula feather full#

'Nature is full of vortices, and the animals and plants use them wisely. But this is the first time that the researchers found the evidence that the effect of the alula is due to a small vortex formed at the tip of the alula feathers. There have been several other attempts to reveal the role of the alula in birds' flight. Measurements of the forces acting on wings in the wind tunnel proved that indeed the presence of the vortex from the alula helps the birds in flight. Although the alula is small, it creates enough vortex to prevent the air flow from being detached from the wing.' says Dr. 'For the wing to fly better, the air has to move closer to the wing. Here they observed that a tiny vortex from the alula tip presses the air flow over the wing and makes the air flow better attached to the wing surface. The alula is the freely moving first digit, a birds 'thumb', and typically bears three to five small flight feathers, with the exact number depending on the species. Then the researchers moved on to the wind tunnel experiments where they visualized the movement of tiny particles around magpie wings. 'But with the alula they seem to turn more easily'.

It is similar to an outboard canted leading-edge flap, which induces an attached LEV on an. Sang-im Lee, the first author of the paper. An alula is a small structure of feathers that prevents birds from stall and flow separation 12, 13. 'It's not that they cannot fly without the alula.' says Dr. They started with observing magpies in the aviary when the birds moulted the alula feathers. The researchers were interested in the flight of magpies. This study was conducted by a research team of biologists and mechanical engineers at the Seoul National University. Why do they use it? How the tiny feathers can help them land softly?Ī recent article published in Scientific Reports says that the secret is a small vortex of air that is formed at the tip of the alula feathers. From countless observations, it has been known that the birds use a small group of feathers, called 'the alula', a thumb-like structure that is present at the bend of the wing, in slow and steep flight such as landing. One mystery of birds' flight is solved! The elegance of birds' flight, their seemingly effortless aerial turns and the softness of their landing, have been envied by many people. The adults typically replace ALL of their feathers in a post-breeding molt, and therefore do not show a molt limit.Image: The alula feathers, the thumb-like structure, on both wings are well visible. Notice the A1 limit in the hatch-year female wing, but not the adult female. Most hatch-year warblers will replace the first (smallest, top) alula feather (A1, indicated by yellow arrow in photos) but not the other two alular coverts, which we refer to as an 'A1 limit'- the molt extended through A1, but stopped before A2 and A3. When aging warblers, we are usually looking at the alula feathers, the coverts at the outer edge of the bend in the wing. Feathers molted after fledging are replaced sequentially and usually the bird is only replacing some wing coverts and body feathers, resulting in feathers of a higher quality (better sheen, more intense color, structurally stronger). Feathers grown in the nest are of a lesser quality because the bird is quickly growing ALL feathers at once.

Most birds will molt (replace) at least some of their feathers after they leave the nest and before migration, resulting in two generations of feathers. We are often asked how we can determine the age of a bird.