Câu hỏi:

Parrots and macaws have become so rare that special varieties of these birds are fetching up to £9,000 each on the black market in Britain. Macaws from Brazil cost from £1,000 and parrots from Australia can cost £7,500 a pair. The demand for parrots, cockatoos and macaws has led to a (1) ______ increase in thefts from zoos, wildlife parks and pet shops. London and Whipsnade zoos are among the many places from which parrots have been stolen. Some thefts have not been (2) ______ in an effort to prevent further incidents. Parrot rustling, as it is known among bird fanciers, has increased rapidly in Britain since 1976 when imports and exports of exotic birds became (3) ______ controlled. Quarantine controls, coupled with the scarcity of many types of parrots in the wild in Africa, Australia, Indonesia, and South America, have caused a shortage of birds which can be sold legally under (4) _____ This has sent prices to (5) _____ levels. Working at night and equipped with wire-cutters, nets and
substances to dope the birds, the rustlers are prepared to (6) _____ serious risks to capture the parrots they want. At Birdworld, a specialist zoo, thieves stole two parrots after picking their (7) _____ through an enclosure containing cassowaries, The cassowary is a large flightless bird, related to the emu, which can be extremely aggressive and has been known to kill humans with blows from its powerful legs.

1. _______