Silkie that are 32 ounces (910 grams). Silkie plumage was once unique among chicken breeds, however in recent years silkie feathering has been developed in several breeds, mostly notably the Chabo, where it is now standardised in Britain and the Netherlands. It has been compared to silk, and to fur. The overall result is a soft, fluffy appearance. Their feathers lack functioning barbicels, and are thus similar to down on other birds. This characteristic leaves Silkies unable to fly. Silkies appear in two distinct varieties: bearded and non-bearded. Bearded Silkies have an extra muff of feathers under the beak area that
Bird-of-paradise lek-type mating system. Others, such as the "Cicinnurus" and "Parotia" species, have highly ritualised mating dances. Males are polygamous in the sexually dimorphic species, but monogamous in at least some of the monomorphic species. Hybridisation is frequent in these birds, suggesting the polygamous species of bird of paradise are very closely related despite being in different genera. Many hybrids have been described as new species, and doubt remains regarding whether some forms, such as Rothschild's lobe-billed bird of paradise, are valid. Birds-of-paradise build their nests from soft materials, such as leaves, ferns, and vine tendrils, typically placed in a tree