We approach thickness of feathers from an axiomatic point of view. We show that our axioms are independent and we use our axioms to establish general properties for arbitrary definitions of thickness which satisfy these axioms. 1. Axioms for Thickness Informally, a feather is a semigroup derivation diagram with the labels on the edges removed. See [2] for a discussion of semigroup derivation di...

IN THEIR BREVIA “FLUORESCENT SIGNALING in parrots” (4 Jan., p. 92), K. E. Arnold and coauthors use mate choice experiments to demonstrate that fluorescence in wild-type budgerigars (Melopsittacus undulateus) is probably functional and not incidental. However, there is further evidence to support this hypothesis in the feathers themselves. The green chest feathers of wild-type budgerigars actual...

We present a model for geometric modeling and rendering of individual feathers for computer graphics purposes. The model represents the feather structure with a collection of parameterized Bézier curves. This parametrization allows easy generation of the existent types of feather structures with biologically-motivated parameters. Once the feather structure is defined, the feathers can be render...

We have performed the structural and optical studies on the iridescent peacock feathers. The periodic structure of the submicron melanin granules has been observed beneath the feather surface and is considered responsible for the optical interference. In addition, the macroscopic structures such as the surface curvature and the configuration of barbules considerably affect the reflection proper...

The aim of this work was the determination of Po, U, U, Pu and Pu concentration in marine birds which permanently or temporally live in the southern Baltic Sea coast. We chose 11 species of seabirds: three species permanently residing at southern Baltic Sea, four species of wintering birds and three species of migrating birds. The results show that analyzed radionuclides are non-uniformly distr...

Despite a wealth of fossils of Mesozoic birds revealing evidence of plumage and other soft-tissue structures, the epidermal and dermal anatomy of their wing's patagia remain largely unknown. We describe a distal forelimb of an enantiornithine bird from the Lower Cretaceous limestones of Las Hoyas, Spain, which reveals the overall morphology of the integument of the wing and other connective str...

Confuciusornis sanctus stands out among the remarkable diversity of Mesozoic birds recently unearthed from China. Not only is this primitive beaked pygostylian (birds with abbreviated caudal vertebrae fused into a pygostyle) much more abundant than other avian taxa of this age but differences in plumage between specimens--some having a pair of long stiff tail feathers--have been interpreted as ...