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
Nest box no outside perches which could assist predators. Boxes may either have an entrance hole or be open-fronted. Some nest boxes can be highly decorated and complex, sometimes mimicking human houses or other structures. They may also contain nest box cameras so that use of, and activity within, the box can be monitored. The diameter of the opening in a nest-box has a very strong influence on the species of birds that will use the box. Many small birds select boxes with a hole only just large enough for an adult bird to pass through. This may be an adaptation to