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Jan Dyck
University of Copenhagen
9Publications
7H-index
515Citations
Publications 9
Newest
#1Richard O. Prum (KU: University of Kansas)H-Index: 46
#2Jan DyckH-Index: 7
Plumage is a complex component of the avian phenotype. The plumage of an individual is composed of numerous hierarchically arranged developmental and morphological modules. We present a hierarchical model of plumage that provides an intellectual framework for understanding the development and evolution of feathers. Independence, covariation, and interaction among plumage modules create numerous opportunities for developmental and evolutionary diversification of feather complexity and function. T...
#1Jens Bursell (UCPH: University of Copenhagen)H-Index: 1
#2Jan Dyck (UCPH: University of Copenhagen)H-Index: 7
Most drab plumage colours are probably cryptic. Crypsis (camouflage) occurs when the colour of a significant part of the plumage is similar to the colour of a significant part of the background against which the prey bird may be detected by a potential predator. In this study we compare back colours of tits and associated species with colour backgrounds in their habitat during a four-month period in winter. We test the hypothesis that in some of the species back colour is similar to one of the b...
#1Richard O. Prum (AMNH: American Museum of Natural History)H-Index: 46
#2Rodolfo H. Torres (KU: University of Kansas)H-Index: 26
Last.Jan DyckH-Index: 7
view all 4 authors...
We conducted two-dimensional (2D) discrete Fourier analyses of the spatial variation in refractive index of the spongy medullary keratin from four different colours of structurally coloured feather barbs from three species of bird: the rose-faced lovebird, Agapornis roseicollis (Psittacidae), the budgerigar, Melopsittacus undulatus (Psittacidae), and the Gouldian finch, Poephila guttata (Estrildidae). These results indicate that the spongy medullary keratin is a nanostructured tissue that functi...
#1Richard O. Prum (AMNH: American Museum of Natural History)H-Index: 46
#2Rodolfo H. Torres (KU: University of Kansas)H-Index: 26
Last.Jan DyckH-Index: 7
view all 4 authors...
The structural colours of avian feather barbs are created by the scattering of light from the spongy matrix of keratin and air in the medullary layer of the barbs1,5. However, the precise physical mechanism for the production of these colours is still controversial1,3,4,6. Here we use a two-dimensional (2D) Fourier analysis of the spatial variation in refractive index of the blue feather barbs of the plum-throated cotinga (Cotinga maynana, Cotingidae) to show that the colour is produced by const...
-Only rarely are green plumage colors due to the presence of green pigments. The best known is turacoverdin. Two galliform species (Ithaginis, Rollolus), Jacana and some anseriform species (Somateria, Nettapus) also have green pigments. The reflectance spectra of plumage pigmented by turacoverdin are characterized by distinct minima at about 570 and 610 nm. These minima represent absorption bands as confirmed by a transmittance spectrum of a turacoverdin extract. Surprisingly, the spectra of the...
#1Jan Dyck (UCPH: University of Copenhagen)H-Index: 7
Existing hypotheses on the evolution of feathers are reviewed with the assumptions that feather evolved from reptilian scales and that pennaceous feathers evolved before downy feathers. Observations with a scanning electron microscope demonstrate that basic to the structure of pennaceous feathers is the lamelliform structure of barbules, the planes of which are oriented at right angles to the plane of the feather vane. Thus the structure of the vane is more open than generally realized. The airt...
#1Hans Ingolf Nielsen (UCPH: University of Copenhagen)H-Index: 5
#2Jan Dyck (UCPH: University of Copenhagen)H-Index: 7
Measurements have been made of the spectral reflectance of the dorsal skin of living tree frogs, Hyla cinerea. The colors assumed by the frogs when placed on backgounds of different col-ors varied with respect to both dominant wavelength (565–580 nm), purity (42–58%) and lightness (2–19%). A certain adaptation to the lightness of the background took place, whereas adaptation to hue and purity seems almost negligible. On the basis of reflection measurements of single chromatophores and chro-matop...
#1Jan Dyck (UCPH: University of Copenhagen)H-Index: 7
The spongy structure in medullary cells responsible for the colour of blue barbs in rump feathers of Agapornis roseicollis and back feathers of Cotinga maynana is studied with the scanning and the transmission electron microscope. The Agapornis structure is an irregular three-dimensional network of connected keratin rods which in many places form rings with outer diameters 0.25–0.3 μ. The air-filled space likewise consists of an irregular network of connected channels. The Cotinga structure cons...
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