نتایج جستجو برای: feathers
تعداد نتایج: 2568 فیلتر نتایج به سال:
—Tachycineta swallows nest in secondary cavities and build nests made of a mat of dry grasses with a nest cup lined with feathers. The insulative quality of feathers may prevent hypothermia of the chicks and increase chick growth, but also may raise the risk of nestling hyperthermia if ambient temperature is high. The number of feathers added to the nest should vary throughout the breeding seas...
For centuries, naturalists have suggested that the tonal elements of pigeon wing sounds may be sonations (non-vocal acoustic signals) of alarm. However, spurious tonal sounds may be produced passively as a result of aeroelastic flutter in the flight feathers of almost all birds. Using mechanistic criteria emerging from recent work on sonations, we sought to: (1) identify characteristics of rock...
Carotenoid-based plumage coloration of birds has been hypothesized to honestly reflect individual quality, either because carotenoids are difficult to acquire via food or because of a trade-off in allocation of carotenoids between maintenance and signaling functions. We tested whether differential foraging ability is a necessary precondition for maintaining individual differences in carotenoid-...
Activity-based models of travel demand have received considerable attention in transportation planning and forecasting over the last few decades. FEATHERS (The Forecasting Evolutionary Activity-Travel of Households and their Environmental Repercussions), developed by the Transportation Research Institute of Hasselt University, Belgium, is a micro-simulation framework developed to facilitate the...
BACKGROUND The holotype of the theropod non-avian dinosaur Microraptor gui from the Early Cretaceous of China shows extensive preservation of feathers in a halo around the body and with flight feathers associated with both the fore and hindlimbs. It has been questioned as to whether or not the feathers did extend into the halo to reach the body, or had disassociated and moved before preservatio...
Colours in feathers are produced by pigments or by nanostructurally organized tissues that interact with light. One of the simplest nanostructures is a single layer of keratin overlying a linearly organized layer of melanosomes that create iridescent colours of feather barbules through thin-film interference. Recently, it has been hypothesized that glossy (i.e. high specular reflectance) black ...
In the chick embryo, large scales (scuta) form on days 9-11 on the anterior face of the shank and the upper surface of the toes; smaller scales (scutella) appear on day 11 on the posterior face of the shank; most of the smallest scales (reticula) form on days 12 and 13 on the plantar surface of the foot. A single injection of 125 micrograms of retinoic acid (RA) into the amniotic cavity caused ...
In this study, we investigated whether bird feathers can be used as a non-destructive biomonitor for organic pollutants. We analysed the outermost tail feathers of 8 terrestrial and aquatic bird species from Belgium (8 species, n=108) for polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and organochlorine pesticides (OCPs). Every compound class could be quantified in one...
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