Silkie as quail and pheasants. Silkies are considered a bantam breed in some countries, but this varies according to region and many breed standards class them officially as large fowl; the bantam Silkie is actually a separate variety most of the time. Almost all North American strains of the breed are bantam-sized, but in Europe the standard-sized is the original version. However, even standard Silkies are relatively small chickens, with the males weighing only four pounds (1.8 kg), and females weighing three pounds (1.36 kg). The American Standard of Perfection calls for males that are 36 ounces (1 kg), and females
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