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Down feathers lack the interlocking barbules of pennaceous feathers, making them very soft and fluffy. The down of birds is a layer of fine feathers found under the tougher exterior feathers. Very young birds are clad only in down. Powder down is a specialized type of down found only in a few groups of birds.
addled eggs Also, wind eggs; hypanema. [5] Eggs that are not viable and will not hatch. [6] See related: overbrooding. afterfeather Any structure projecting from the shaft of the feather at the rim of the superior umbilicus (at the base of the vanes), but typically a small area of downy barbs growing in rows or as tufts.
Newly hatched chicks have downy feathers that do not become waterproof until the chicks grow into juveniles. [20] The juvenile plumage, attained by thirty days after a chick hatches, is dark brown or gray above and white below. These feathers are mainly needed to protect the chicks from the strong sun rather than keep them warm.
The calamus is hollow and has pith formed from the dry remains of the feather pulp, and the calamus opens below by an inferior umbilicus and above by a superior umbilicus. [2] The stalk above the calamus is a solid rachis having an umbilical groove on its underside. Pennaceous feathers have a rachis with vanes or vaxillum spreading to either side.
Feather variations. Feathers are epidermal growths that form a distinctive outer covering, or plumage, on both avian (bird) and some non-avian dinosaurs and other archosaurs. They are the most complex integumentary structures found in vertebrates [1] [2] and an example of a complex evolutionary novelty. [3]
The tips of these feathers are waterproof and help protect the bird from the elements, while the inner parts of the feather near the bird's body are more downy. Wing contour feathers (known as coverts) help with the aerodynamics of the wing by covering where the flight feathers attach to the bone.
A similar edible tunicate in the Mediterranean is Microcosmus sabatieri, also called a sea violet or sea fig. [11] There are concerns about the safety of eating P. chilensis, given its high concentration of vanadium, with up to 1.9 mg/kg found in dry blood plasma. [12] Vanadium is a heavy metal, considered toxic at any more than incidental ...
The nominate race, E. h. helias, is found east of the Andes in lowland tropical South America, from the Orinoco basin, through the Amazon basin and Pantanal. The subspecies E. h. meridionalis , has a more restricted distribution, being found along the East Andean slope in south-central Peru , in the lower subtropical zone at altitudes of 800 ...