英国有一个由来已久的牛奶递送系统，送奶工开着小卡车把瓶装的牛奶送到各家各户的门口。 20世纪之初，奶瓶都没有盖子，鸟很容易就能吃到瓶口的乳脂，山雀和红知更鸟学会了从瓶口吸取乳脂。 　　后来，在第二次世界大战期间，英国的送奶工用铝箔封住了奶瓶口。到了 50年代，英 The United Kingdom has a long-standing milk delivery system where milch workers drive small bottles of bottled milk to the doors of households. At the beginning of the twentieth century, the bottle had no lid, and the bird could easily get to the mouth of the bottle. The tits and the red robin learned to suck the cream from the mouth. Later, during the Second World War, the British milkman sealed the bottle mouth with aluminum foil. By the 1950s, Britain