22 Feb. 1982|
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The piece uses nice woods, an adjustable counter-balance system, and clever magnetic hinges. Argentavis magnificens from the upper Miocene (6 million years ago) of Argentina, with an estimated mass of 70–72 kg and a wingspan of 7 m, was the world's largest known flying bird.
The tubenoses of albatrosses and other Procellariiform birds resemble pitot tubes and may function in the same way. Bounding flight is not seen in birds of greater than 300 grams, thus likely to be constrained by size.
Hummingbirds flying in the rain -- Flight in rain represents a greater challenge for smaller animals because the relative effects of water loading and drop impact are greater at reduced scales given the increased ratios of surface area to mass. Flying in a flock comes at a cost -- Flying birds often form flocks, with social, navigational, and anti-predator implications.
At low speeds, airflow over wings is relatively slow and, to maximize lift, birds must maximize the angle of attack and flap their wings fast to increase air speed and this requires lots of power.
Waddling makes most of penguin's short legs - It may not be graceful, but the penguin's waddle makes perfect sense to scientists, who found that the bird's side-to-side gait conserves energy. Avian head bobbing -- Many species of birds move their heads forward through a series of successive, fixed positions when walking. Birds adapted for climbing, like woodpeckers and treecreepers, have sharply recurved claws and toes, sometimes relatively long, that can be spread apart to help firmly grip the substrate (typically tree bark). Surprisingly, this species has one of the widest breeding distributions of all diving birds, and does not require more food than these other species.
It was probably a diurnal predator, dependent on thermals for flight activity for much of the time much as large, broad-winged carnivorous birds we see today.
The forward-pointing nostrils or tubenoses (pointing in the direction the birds fly), that could measure stagnation or pitot pressure, lead into nasal chambers also connected to the mouth, or oral, cavity, where pressure would correspond to static pressure.
The small birds which most frequently utilize bounding tend to have short rounded wings (low aspect ratio), poorly suited for gliding, making undulating flight less aerodynamically attractive. Further, flying in a flock can result in aerodynamic benefits, thus reducing power requirements, as demonstrated by a reduction in heart rate and wingbeat frequency in pelicans flying in a V-formation. University of California researchers found that the gait works like a pendulum, with energy stored at the end of each swing for the bird's next step. Foraging woodpeckers and treecreepers approaching the top of one tree, typically fly downward to a lower position on another tree then again climb upwards and, when approaching the top, repeat the process. In slope soaring, a bird flies in a region of rising air caused by upward deflection of wind over a ridge or a cliff.
This method of soaring requires that these birds be able to detect variation in wind speed at various distances above the ocean surface.
Phil Battley, an ecologist at Massey University, said it had been suspected that the birds could fly such distances but now it had been proved.
Head movements nevertheless play essential roles in vision, giving visual cues for distances and relative locations of objects, providing an opportunity for changes in head angle, and permitting birds to fixate new objects of visual interest.
Climbers that typically move up trees, like woodpeckers (Picidae) and treecreepers (Certhidae), have relatively short legs (particularly the tibotarsus) that keep their center of mass close to the substrate and a long, stiff tail that provides support against the force of gravity.
Not only does such a foraging strategy make sense energetically (because flying downward is less costly), but attempting to move downward when foraging would create at least three problems (Norberg 1981): (1) difficulty in seeing where to grasp the bark after a hop, (2) the stiff tail could get caught on the irregular surface of the bark, and (3) potential prey would be alerted to the presence of a possible predator before the bird could get in a position to capture them.
If the sinking speed of the animal is less than the velocity of the rising air, the bird is able to remain airborne indefinitely without flapping its wings.
V-formation flocks are limited to moderately steady flight in relatively large birds, and may represent a special case. No direct evidence has been published showing that birds favor the stabilization phase while foraging either for moving or immobile food.
Upstroke thrust, drag effects, and stroke-glide cycles in wing-propelled swimming by birds. Pitot tubes on airplanes have two holes, one pointing forward (in the direction of the plane is flying) to measure what is called the stagnation (or pitot) pressure, and a side hole that measures static pressure (the ambient pressure of the surrounding air).
Flying in the rain: hovering performance of Anna's Hummingbirds under varied precipitation. The difference between the stagnation pressure and static pressure is called the dynamic pressure, which can be used to determine a plane’s airspeed. By contrast, birds hovering in heavy rain adopted more horizontal body and tail positions, and also increased wingbeat frequency substantially, while reducing stroke amplitude when compared with control conditions. For example, in the diagram below, as a plane increases its airspeed, the pressure generated at the stagnation point will increase relative to the static pressure and the fluid in the differential manometer will be forced downward, out of the manometer, and upward in the tube leading out of the manometer. Therefore, unlike V-formation pelicans, pigeons do not gain an aerodynamic advantage from flying in a flock. The researchers coaxed penguins across a force platform -- "kind of a fancy bathroom scale," says Griffin -- with bits of fish.