Bird nest July to September), it is not in others, and the swiftlets are declining in areas where the harvest reaches unsustainable levels. Some species of birds are also considered nuisances when they nest in the proximity of human habitations. Feral pigeons are often unwelcome and sometimes also considered as a health risk. The Beijing National Stadium, principal venue of the 2008 Summer Olympics, has been nicknamed "The Bird Nest" because of its architectural design, which its designers likened to a bird's woven nest. In the Victorian era, naturalists often collected bird's eggs and their nests. The study of bird nests is
Neotropical Birds Online available, photographs of the species, its habitat, and of the nest and eggs. Also provided, when available, are recordings of the species' song and calls, selected from the collection in the Macaulay Library at the Cornell Lab of Ornithology and from other online sources, such as xeno-canto. Neotropical Birds Online Neotropical Birds Online is an online encyclopedia whose subject is the bird species that breed in the Neotropics. "Neotropical Birds Online" is patterned after "Birds of North America". Each account profiles a single species, and the accounts are published in the order in which they are completed. The project is