According to Wild Birds, published by the Audubon Society of America, as long as local people leave them undisturbed many birds will migrate from their natural habitat to human surroundings because these tend to harbor fewer natural predators.
根據美國奧杜邦生物保護協會出版的「野生的鳥」一書指出，只要當地的人活動不多，不會對它們造成騷擾，許多鳥會從自然環境移居到人類的環境中，因為在靠近人煙的地方，其他天敵較少。