Female owls will generally lay one to fourteen roundish white eggs. Females from different owl species lay different numbers of eggs. The number also depends on how much food is available. For example, if the nearby mouse populations in high, a female short-eared Owl might lay ten eggs. If the mouse population is low, she might lay just four eggs.
Eggs are usually laid one to four days apart. The female owl sits on the eggs to keep them warm. This is called incubation. During the incubation period, the female loses the feathers on her belly in order to transfer more body heat to the eggs.
She presses the warm bare skin, or brood patch, against the eggs. She lies on the nest in the incubation position, with her head low and stomach down, keeping the eggs warm all the time. Baby owls, called owlets or nestlings, hatch 22 to 40 days after the eggs are laid. Because eggs are laid of different days, owlets break free from their shells on different days.
This is called asynchronous hatching. The first owlets to hatch can be one to two weeks older than the last ones to hatch. When young owls hatch, they are covered with white, downy feathers and their eyes are closed.
Several days after hatching, their feathers turn gray and their eyes open. When the female sits on a nest of hatched chicks it is called brooding.
For the first couple weeks of life owlets are helpless; they are unable to see, fly, or thermoregulate maintain their own body temperature. Their mother broods them by keeping them safely under and around her in the nest. Male owls hunt and bring food to the nest.
Female owls tear small pieces of meat off the prey animals and feed them to the nestlings. Owls grow up quickly. In just three or four weeks, the owlets start to eat prey animals whole and spit up pellets. Nestlings compete with each other for food. Because the older nestlings are bigger and stronger than those born a few days later, they often get most of the meat. If food is scarce, the younger owlets may even starve to death. When the owlets are two to three weeks old, both parents may leave the nest to hunt.
The owlets cry out to their parents for food; these are called food begging calls. The text for the Adaptations page comes from the children's book. This usually happens once a year, beginning after the parent birds have raised a brood that has fledged and can care for themselves. The process takes up to 3 months, during which feathers are shed and re-grown over the entire body in a regular pattern.
With the exception of the Barn Owl, molting of wing feathers is from the inside out. Barn Owl wing feathers are replaced from the middle of the wing out in both directions.
Tail feathers also drop out a few at a time, except in some smaller Owl species, who loose all the tail feathers at once. When birds molt, new feathers grow to replace the ones that have fallen out. The new feathers immerge from the skin tightly bound in a thin shaft of tissue. These are called pin feathers. The shaft splits shortly after, allowing the new feather to unfurl and grow to its full size. Most owls have relatively large, rounded wings. The wings are broad, with a large surface area relative to the weight of the bird i.
All together, these feather features enable owls to remain undetected when they fly. See and hear the difference between a flying owl and other birds in this video , and check out this KQED Deep Look video to learn more and see owl feathers up close. Please enable cookies to view this embedded content! Click here to open your preferences and accept cookies.
DinoTail Next Generation from Siemens Gamesa has fine combs and serrated edges that help to reduce turbulence and noise while increasing power in wind turbines. An aerofoil from City University of London has finlets that stabilize flow and reduce turbulence.
As mentioned above, Neuhaus et al. One explanation might be that in cruise flight conditions the stagnation point at the leading edge results in a relative low air flow through the serrations due to the low air stream velocity.
At sharp angles of attack, however, serrations comb through the air like a plough through a field. By their bending and orientation, serrations induce tiny vortices running over the dorsal wing surface as shown by Ito This phenomenon increases the lift and reduces the noise of barn owl wings during flapping flight and striking, which is extremely useful for the owl. Interface Focus 7: Uneven, complex oyster reefs create protective crevices where calm waters allow larvae to attach and thrive.
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