One negative result of people’s interference with the environment is that many kinds of animals are becoming rare. In fact, their numbers are decreasing so rapidly that they are in danger of being extinct. Because worried and concerned experts want to make sure that these animals do not disappear, an "endangered species" list has been made, and ways to save them have been started. Some types of birds, like eagles, are in danger of extinction. This is the reason why many concerned citizens have organized into groups to try to save the birds. The National Audubon Society (NAS) is one such organization. The people of the NAS, ironically, once tried to encourage interest in birds. The present situation indicates that they Were too successful. Nowadays the same people are looking for ways to protect the birds from the people who want to watch them. Just a few years ago, bird watchers were stereotyped as harmless but strange: people thought of all bird watchers as eccentric hunters who chased their prey with binoculars to see better with, instead of guns to shoot with. Stereotypes of bird watchers were the subjects of jokes because the general public did not find birds interesting. However, with a little education and advertising, bird watching and bird watchers really changed. Bird watching became a national pastime, an interesting hobby, a favorite way to spend leisure time. Because of the efforts of the NAS, the numbers of amateur ornithologists(鸟类学 者) have multiplied. Now between five and ten million non-professional bird watchers search for a glimpse of a golden pheasant, a pygmy swift, or a whooping crane. In the past decade, the NAS membership has quadrupled; such an increase of four times the number in only ten years indicates a surge of enthusiasm for birds. Unfortunately, this great growth of interest has meant another kind of interest: the over-enthusiasm of some amateur ornithologists has resulted in harming the birds and their habitats, the special environments that the birds choose. For example, both vegetation and the nesting places have been trampled; the natural places have been destroyed by the feet of the small percentage of overly enthusiastic watchers. One professional ornithologist reported that so many people have become interested in birds that one rare bird can bring a flock of bird watchers. A result is that where there were once flocks of birds, there are now only a few. Which word best describes the author’s attitude toward people’s enthusiasm in birds