经济学人下载:英国鸟类迁徙趋势 有所改变

Ornithological trends
英国鸟类迁徙趋势

This bird has flown
有所改变

Why some species are thriving outside southern England
为什么英格兰南部有些物种开始兴盛？

WHEN people talk about a “north-south divide” in Britain they are usually referring to house prices, employment and the ratio of private-sector to public-sector jobs. The south scores higher on all such measures. But new data from the British Trust for Ornithology (BTO), a research charity, hints at the growth of another north-south divide—this time to the north's benefit.
在英国，当人们提到“南北分歧”的时候，他们通常指的是房价、就业和私企与国企就业率之比。在所有类似的测量标准中，英国南部地区的数据较高。但慈善研究机构英国鸟类研究信托公司提供的新数据表明，在另一种形式增大的南北分歧中，北部地区获益较大。

Every 20 years the BTO produces a superbly detailed atlas of bird life in Britain and Ireland. The 2007 to 2011 edition is cheery: more species are tallied than in previous atlases, and many birds are increasing in number. Compared with two decades ago, 45% of regular native species are ranging more widely while 32% are living in smaller areas; the rest have stayed put. But the most striking news comes from the north.
每隔20年，英国鸟类研究信托公司都会公布一组有关英国和爱尔兰的鸟类生活详细地图分布册。2007-2011年的地图分布册显示的数据令人振奋：与前几年相比，记载了更多的物种；许多鸟类数量也有所增加。与20年前相比，45%的常规本地物种活动范围扩大，32%生活范围缩小；剩余的物种保持稳定。此外，最令人惊喜的消息从北部地区传来。

The overall populations of woodland, farmland and migrant perching birds are up in northern England and Scotland but down in the south. The same is true of individual species such as the garden warbler, bullfinch and swallow. The number of cuckoos, a closely-watched species, declined by 63% in England between 1995 and 2010 but by only 5% in Scotland. Raptors are faring especially well in the south, but their numbers are rising in most parts of Britain.
林地、农田和中途停留的迁徙鸟类数量在英格兰北部和苏格兰有所上升，但是在南部地区却有所下降。相同的情况也适用于个别物种，如园林莺、红腹灰雀、燕子。常见的物种之一杜鹃的数量，从1995年到2010年下降了65%，但在苏格兰地区仅下降了5%。南部地区的猛禽在南方生活的尤其滋润，其数量在英国大部分地区都有所上升。

Partly this reflects climate change, suggests Simon Gillings of the BTO. Some birds are drawn to warmer winters in Scotland and northern England; visiting migrants may stick around for longer. Hard though it may be to believe during a week of torrential rain, the south is becoming drier, pushing snipe northward. More efficient farming has squeezed some farmland species.
英国鸟类研究信托公司的西蒙·格林斯认为这部分反映了气候变化。有些鸟类迁往苏格兰和英格兰北部等冬天较为温暖的地方；旅鸟停留的时间可能会更长。我们很难相信在一周的强降雨之后，南部地区变得更加干燥，使得物种向北部迁移。高效率的农耕方式也使得一些农田物种的数量降低。

Some birds find it harder to make homes in the south, too. Pressure on housing means dilapidated buildings and barns, handy for nesting, have been converted into human dwellings. Between 2006 and 2012 the number of vacant dwellings fell by 17% in London and by 12% in Kent. Over the same period the number of empty houses increased by 16% in Derbyshire and by 10% in Lancashire. Northern mining villages once full of workers are now sparsely populated, points out Ian Bartlett, a birdwatcher in Hartlepool, in north-east England. They have become hot spots for birds and the people who watch them.
有些鸟类也发觉在南部地区繁衍更为艰难。以往适宜筑巢的荒废建筑物、谷仓都被人们的住房所占领。2006年至2012年，伦敦的房屋空置率下降了17%，肯特郡的下降12%。同一时期，德比郡的房屋空置率上升16%，而兰开郡的上升10%。哈特尔普尔的鸟类观察员兰·巴特勒称，位于英格兰东北部的北部采矿型乡村曾一度人满为患，现在人烟稀少。

Cultural difference also plays a part, thinks Mark Cocker, an expert on birds. The “obsession with tidiness” is stronger in the south, he says. Fewer people cultivate gardens; they prefer to cover them in decking and remove weeds from between concrete slabs. Village greens are mowed short. In contrast, Scotland and northern England have more trees, grassland and wind-swept moors. Less popular with humans, rugged parts of the countryside are filling up with a winged population instead.
鸟类专家马克·科克尔认为，文化差异也起了一定的作用。他表示，南部地区的人们“痴迷于整洁”的表现更为强烈。很少有人整理花园，他们更喜欢在花园装饰木甲板，在坚硬的石板中间除草。村庄草地也经常修剪得整整齐齐。相反，苏格兰和英格兰北部地区拥有更多的树林、草地和荒凉的沼泽地。很多崎岖的乡村人烟稀少，而鸟类却在此扎根，欣欣向荣。