经济学人下载:鸟类数量锐减 是天灾还是人为?

Britain Bird numbers
英国 鸟类数量

Out of the woods
离开树林

Good news on the bird population—but not for everyone
鸟类数量的捷报——但并非对所有人

City Slicker
城市人

British birdwatchers are used to bad news. House sparrow numbers have fallen from an estimated 30m to 10m since 1966. Curlews have become a rare sight, their numbers plummeting by 50% in 15 years. Cuckoos, once-frequent visitors from Africa, have declined by 63% in the south-east in the past two decades. Earlier springs that confuse migratory birds, more efficient farming and the conversion of dilapidated buildings (good for nesting) into modern homes have all contributed to these woes.
英国的观鸟者已经对坏消息习以为常。自1966年以来，家养麻雀的数量已从约3000万减少到1000万。杓鹬的数量在十五年间锐减50%，变得越发罕见。过去二十年间，曾经经常从非洲迁徙至英国东南部的布谷鸟数量减少了63%。造成这种灾患的原因包括迷惑候鸟的早春，更高效的耕种以及危房（适宜筑巢）向现代房屋的转变。

But data released by the British Trust for Ornithology (BTO), a research charity, suggest some are soaring. Tracking bird populations by means of regular surveys, the figures give the clearest picture yet of 49 species acrossBritain.
但是公益性科研机构英国鸟类学基金会公布的数据显示，有一些鸟类的数量却扶摇而上。他们通过定期调查的方式追踪群鸟，其数据清晰地描绘了目前全英49种鸟类的真实状况。

Blackcaps, small woodland birds native to Germany and eastern Europe, are lingering after their summer sojourns: since 1967 numbers have increased by 177%. The little egret, a white heron-like bird, arrived from continental Europein 1989 and now numbers over 5,000. Wood pigeons, once found shyly cooing in forests, have boldly moved into cities and suburbs.
黑顶林莺是来自德国和东欧地区的一种小型林栖鸟，在它们的夏季之旅后仍然流连忘返。自1967年以来，它们的数量增加了177%。小白鹭，一种白色的鹭科鸟类1989年从欧洲大陆而来，现在它们的数量已经突破5000. 原先只敢在树林里低吟浅唱的斑尾林鸽已经勇敢地迁移到了城市和郊区。

Environmental and agricultural changes have helped as well as disoriented birds. Modern farming techniques allow grain to be sown in the autumn rather than the spring; that helps wood pigeons feed in winter. Warmer winters mean rivers and ponds are less likely to freeze, providing the little egrets with food. James Pearce-Higgins of the BTO says that blackcaps benefit particularly from the increasing popularity of berry bushes (such as rowan and yew) in people’s gardens.
环境和农业的变化既帮助了鸟类，也迷惑了它们。相较春天播种，现代的农业技术使秋天播种成为可能，这也为斑尾林鸽过冬提供保障。暖冬意味着河流与池塘难于冰冻，这给小白鹭提供了食物。英国鸟类信托基金的詹姆斯皮尔斯—希金斯说，人们花园中越来越多的浆果丛（诸如欧洲花楸和紫杉）令黑顶林莺获益良多。

These species and others benefit from the British love of bird feeders. “I would be amazed if anyone feeds garden birds inEuropeas much as we do,” says Stephen Moss, a nature writer. First sold in 1964 by the Royal Society for the Protection of Birds (RSPB), a charity with over1mmembers, bird feeders took off in the 1990s when food such as sunflower hearts and nyjer seeds became widely available and the RSPB began to encourage people to feed birds throughout the year. (The bird tables found in other northern European countries, such as Finland and Germany, tend to be stocked only during the winter.) In 1987 only 17 species availed themselves of British feeders; these days 86 do.
以上几种和其他种类的鸟获益于喂鸟者的英式关爱。“在欧洲，没有人会像英国人一样频繁地在花园喂鸟了。”自然作家史提芬摩斯说。喂鸟器最早在1964年由皇家鸟类保护协会出售，该协会是有超过百万会员的慈善组织。在90年代，葵花籽、蓟花籽之类食品的广泛普及，同时皇家鸟类保护协会鼓励人们全年不休地喂鸟，喂鸟器的销量突飞猛涨。（在北欧的一些国家，例如芬兰和德国，喂鸟台只在冬天发挥作用。）在1987年，只有17种鸟得到了喂鸟者的帮助，而今有86种。

Birders grouse nonetheless. Some of the species prospering, such as carrion crows and buzzards, are disliked. And migratory birds that extend their visits may provide competition for some avian natives. They are “muscling in and getting the first claim on breeding sites”, says Richard Cowser of the Sussex Ornithological Society. Like their human counterparts, residents of a small island buffeted by global winds, British birds will have to learn to compete.
然而怨声随之而起。一些不遭人喜欢的鸟也开始泛滥，比如食腐乌鸦和秃鹰。同时，逗留时间更长的候鸟也可能对一些本土鸟产生竞争。据苏塞克斯鸟类学社团的理查德 考瑟所说，它们“强势插入，占领繁殖地。”就如它们的人类伙伴一样，小岛上的居民被全球风席卷。英国的鸟类要学会竞争。