原文: Berry Wars

Berries - they grow on trees, bushes, climbing plants and on shrubs at ground level. In the British Isles alone, more than sixty species of native plants produce them. Animals love them, especially birds. Thrushes and berries go together like ice cream and August but these wild fruits are an equally important ingredient in the diet of black grouse and capercaillies (bilberries). In the Arctic, even large mammals such as polar bears gorge for days on blueberries. For birds, the range of berries and the extended length of the season during which various types become available - from cherries and elderberries in July to holly and ivy long after Christmas - means that many songbirds switch from a summer invertebrate diet to a winter one based on berries. When cold weather arrives, frozen ground prevents foraging for worms, grubs and fallen seeds, leaving berries as a nourishing lifeline. What's in this for the berries?  
 
  Birds and berries are a remarkable example of interaction in nature. The fleshy pulp of a berry contains starchy carbohydrate which conceals and protects the seed within. Most berries are also full of vitamins. Rose hips contain concentrated vitamin C, still used as a medicinal syrup. All this is packaged in bright, glossy colours designed to attract diners. Birds eat the produce and spread the precious seeds contained in the berry over a wide area. They drop or excrete the undigested seeds enabling the plant to spread.  
 
   However, seed-spreading doesn't work when tough-billed species crack open berries and eat the seeds. Not to be outsmarted, hawthorns and other shrubs manufacture rock-hard seeds that pass through avian digestive systems unscathed. Yew berries are delicious but have a poisonous coating on the seed. This is designed not so much as a deterrent, but as a means of ensuring that customers eat the fruit and then spit out the bad-tasting seed.   
 







  Champion berry-eaters are blackbirds, song thrushes, mistle thrushes and - arriving for the winter - redwings and fieldfares. Roving bands scour the countryside. If the weather is mild they alternate between feeding on earthworms with time spent stripping berries from hedgerows. Feeding is en masse but not necessarily cooperative. Sticking together in a flock confers safety and a shared desire to locate feeding areas. However, when a crop of berries is pinpointed it is everyone for themself. Mistle thrushes are an exception. They prefer to defend a berried tree against all-comers.  
 
  Their motives for this behaviour are two fold. First, they want the berry supply as a larder that will see them through the winter. This means that while they protect it fiercely, they may not actually begin eating the food for some time. Secondly, if hard times do not materialise then the birds gain a great advantage in having food available at the end of the winter, enabling them to nest early. Although 'prudence' seems to be their middle name, protectionist plans can go awry if a visiting horde arrives. Mistle thrushes may be pugnacious, but defence against dozens of ravenous redwings and fieldfares is hopeless.  
 
  Starlings, as befits one of the most successful birds on Earth, are not averse to exploiting a berry crop - particularly elderberries in late summer and autumn. Starlings are systematic in their approach and methodically strip bushes from the top down. They also drop far fewer berries than other birds and leave bushes picked completely clean. However, for once, they are left in the shade by waxwings, a close relative from the vast coniferous belt extending across northern Europe and into Russia  
 
  There is no doubt about it - waxwings look stunning. The soft brown plumage has a texture like velvet; they have insuppressible crests and a face pattern to inspire a make-up artist. In Dutch they are named 'pestvogel' meaning invasion bird. This is apt. Waxwings are famous for two attributes: sporadically irrupting across western Europe during winter and, when they get here, feasting on berries. Although they feed by flycatching for mosquitoes during the summer, the species is exclusively a berry-eater throughout the rest of the year. Flocks fly west in a nomadic quest for grub, which means their movements are unpredictable.   
 
  Waxwings pluck and swallow berries whole and then retire to digest lunch before flying back to plunder more haws, hips or any red berries growing on ornamental shrubs. They are not fussy, so flocks are as likely to alight in a cotoneaster bush in a city park as on a rural hawthorn hedge. Hailing from northern forests, they know little of people and have the endearing habit of being almost wholly indifferent to human approach.
Just how many berries do they eat? In early 2001 an unprecedented flock of 500 waxwings spent four winter months devouring cotoneaster berries in Belfast's city parks and housing estates. Based on counts made over several days, individuals consumed a daily average of 500 apiece (twice the body weight). This is in line with similar estimates elsewhere. Doing maths was never such fun. How many berries did the flock go through in the 100 days between Christmas and mid-April? The astonishing answer is 25 million! 
 

译文: 果实之战

果实生长在树木、矮树、爬藤植物和地面灌木丛上。单在大不列颠群岛上，就有60多种植物能够结出果实来。动物们喜欢果实，特别是鸟类。画眉与果实的关系就好比冰淇淋和盛夏那般密切，不过野生果实也是黑松鸡和大雷鸟重要的食物成分。在北极，甚至是北极熊这一类大型哺乳动物一段时期内都得依靠蓝莓来果腹。对于鸟类而言，果实生长的范围大小和季节长短（从夏天的樱桃、接骨木果实到冬天的长春藤）是非常重要的。许多鸣禽夏日中可以捕食一些软体小动物，冬日里则只能以果实为生。当寒冬到来时，结冰的地面上不可能搜寻出蚯蚓、幼虫和掉落的种子，只有果实才能提供养分，维持生命。其中的奥妙何在呢？

鸟类和果实是自然界生物链上一个非常突出的实例。果实中的果肉肉质厚实，含有淀粉碳水化合物，对包裹在其中的果核起到一定的保护作用。大部分果实都含有大量的维生素。至今仍作为医用糖浆之用的野玫瑰果蕴含了极为丰富的维生素C。最外层色彩鲜艳、富有光泽的果皮则吸引着食用者。鸟儿们吞食果实，并把包裹在其中的珍贵种子通过吐核或排泄的方式播种在辽阔大地上。

不过，有着坚硬喙的鸟儿则是破开果实，取核食之；那么以上的播种方式就没什么效果了。没关系，兵来将挡，水来土掩。山楂和某些灌木的果实有着岩石般坚硬的果核，就算经过了鸟儿的消化系统也完好无损。紫杉果实虽味道甜美，但其果核外层有毒。这点无损它的食用性，但可以确保食用者在享用的过程中把味道不好的果核吐出来。

果实的吞食大王有燕八哥、歌鸠、槲鸫及红翼鸫和田鸫。它们盘旋搜索着整个乡村。天气好的话，它们会捕食蚯蚓，并时不时地从灌木树篱上剥下果实。进食可以是集体活动，但不一定非得是合作性的。群聚给予了安全性，且大家都希望共同寻找食物区。然而，当果实收成很小时，则是大家共享的。槲鸫是特例，它们更乐意独占一棵结满果实的树，而驱赶所有的靠近者。

这种行为的动机有两个方面的。首先，槲鸫把这棵果树作为一个食物储柜，以便度过整个冬天。也就是说在它们激烈保护这棵树的同时，暂时也不会吃掉这些果实。其次，如果环境不是太糟糕的话，末冬里这些鸟儿在食物拥有上占据很大优势，使得它们可以早些筑巢。虽然“谨慎”似乎是它们的特点，但若有一群鸟儿到来，它们的保护计划将落空。槲鸫此时也许变得非常好斗，但与一群贪婪的红翼鸫相抵抗是不可能的。

欧掠鸟，地球上生存适应最为成功的一种鸟，很乐意开采果实，特别是夏末和秋末的接骨木果实。欧掠鸟采摘的方法很有条理性，从上至下有序地剥离灌木。灌木上的果实被它们采摘得很彻底，而且掉落的也比其他鸟儿少。然而，它们有时也会败在连雀（欧掠鸟的近亲，来自于穿越北欧延伸入俄罗斯的广袤针叶地带）手下。

 连雀看上去就棒极了，这点无需置疑。柔软的褐色翅膀有着天鹅绒般的质地；高高耸起的冠和面容足以激发化妆家们的灵感 。在荷兰，它们被称作“psetvogel”，意为侵略之鸟。这很贴切。连雀以两个特征而著称：冬天里会零星地突然冲入西欧以及享用果实。虽然夏天里它们以蚊子为食，但其它时候都专门吃果实。出于对幼虫的不定需求，连雀会举群向西飞行，这就意味着它们的活动是不可预知的。