世界最大雀巢 你不知道的群织雀

　　Africa’s incredible social weaver, about the size of the sparrows, come together in colonies of as many as 500 individuals to build by far the most enormous nests on Earth, at more than 2,000 pounds and 20 feet long by 13 feet wide by 7 feet thick. The structures are so big they can collapse the trees they’re built in, and so well-constructed they can last for a century. Occupying as many as 100 chambers, these are quite possibly the biggest vertebrate societies centered around a single structure—outside of human beings and their skyscrapers, of course.

　　非洲的群织雀大概和麻雀一般大小。500只群织雀聚居在一起，修建了世界上最大的窝巢——它重达2000磅，长20英尺，高7英尺。这个巢穴是如此的巨大，以至于它可以拖垮一棵大树;而且修建精良可以留存一个世纪。巢穴里大约有一百个房间，这大概是围绕着一个中心结构的脊椎结构的社会了——当然，除了人类和他们的摩天大楼。

　　Calling the semi-arid plains of Namibia and South Africa its home, social weavers make use of several different materials, building the nest by weaving in twig after twig. Then they line the insides of the chambers with luxurious grass and feathers and, occasionally, cotton balls.

　　以半干燥的纳米比亚平原和南非为家，群织雀利用不同种类的材料，一个树枝一个树枝地织起它们的巢穴。一间间房里铺着奢华青草和羽毛，偶尔还有棉球出现。

　　The weavers will pack into the nest’s chambers three or four at a time, and when they do, the benefits of the enormous structure become clear. Winter nights here regularly dip below freezing, even down under 20 degrees Fahrenheit in the coldest places. At one point in his field work Leighton dropped thermal recorders into chambers, which weavers later that day took up residence in.

　　通常一间房里会挤进3~4只群织雀，而这时，这个巨大的建筑的好处就相当明了了。冬夜总是凛冽的，在最寒冷的地方有时甚至会达到华氏20度。莱顿在鸟巢里放置了一个热式记录仪，而后鸟儿入住了该巢穴。

　　“I think the nighttime temperature was 30 or 35, and the temperature inside the chamber with three or four birds in it was 70 or 75 degrees Fahrenheit,” he said. “So there’s this really huge thermal benefit to staying in these giant nests.” In the baking summer, too, the chambers provide the birds with a fairly tolerable climate both day and night. Far from the top of the nests, which bake in the sun, the chambers enjoy the shade. And the nest as a whole lags behind the ambient air temperature a bit like a swimming pool, whose waters retain the cool of the evening into the morning and the heat of the afternoon back into the night.

　　“夜间的温度大约是30~35华氏度，但是住着三四只群织雀的房间温度可以达到70~75华氏度。”他说，“因此这些巢穴的保温作用非常明显。”而在炙热的炎夏，房间依旧可以为鸟儿提供舒适的环境。房间远离巢顶，就意味着远离了太阳而享受音量。而且房间像一个游泳池一样把热空气隔离开，它会会在晚上储存凉意以抵御白天的热量。

　　The perks don’t stop there. According to Leighton, by situating the chamber entrances at the bottom of the nest, the birds also likely protect themselves from predation by hawks flying above. And this positioning also helps keep water out. And from an evolutionary perspective, living in such big groups boosts an individual’s chances of not getting picked off by a predator.

　　特别待遇还不止这些。莱顿说，鸟儿把房间的门设在巢穴的底部，这样它们也可以躲避老鹰的袭击。而且也可以防止巢穴里的洪涝。而且从进化的角度来看，群居降低了它们被捕食的机会。

　　The social weaver’s setup is so sweet that other species are more than happy to squat in their digs. African vultures are fond of hanging out on the roof, and red-headed finches will raise their families in the chambers. But in some time they’ll kill the landlord. “it has been documented that pygmy falcons will sometimes eat social weavers,” said Leighton. “Which is kind of a depressing thought, because social weavers are building and maintaining this giant apartment complex, and then a predator moves in and starts eating them.”

　　群织雀的巢穴实在太可爱了，以至于吸引了不少其它的动物。非洲秃鹫喜欢把自己挂在屋檐上，红头雀会在房间里养育子女——但有时它们会杀掉原本住在里面的群织雀。“有档案记载，红头雀有时会吃掉群织雀。”莱顿说，“虽然很不愿意这样说，但是群织雀辛辛苦苦建造、维护它们的家，然而建成之后侵略者就席卷而来把它们吃掉。”

　　That’s not to say social weavers don’t stand up for themselves. Should a snake wander up the tree or a pygmy falcon land on their roof, they’ll crowd around the menace and fire out high-pitched alarm calls—incessantly. While this may scare away smaller birds, it does little good on falcons and serpents.

　　然而，这并不意味着群织雀不会奋起反抗。如果有蛇试图爬上树来，或者一只红头雀逗留在屋顶，它们都会群拥而出发出不停地发出高音警报。然而这可能会吓跑小只一些的鸟儿，却赶不走红头雀和大蛇。

　　Social weavers can also fall victim to their own success. While some nests may stand for decade after decade, others can get so waterlogged in the rainy season that the trees that support them collapse under the weight. “And actually the nest I was working on, this most recent summer the entire tree just fell over,” said Leighton. “It ruined part of the nest, but some of the tree limbs that are still sticking out of the ground.”

　　此外，巢穴的成功也有可能给它们带来危险。一些巢穴可能会留存数十年，因此在雨季会浸水变重，使得大树无法承受它们的重量而倒塌。“就我研究的巢穴来看，最近一个夏天整棵树都倒塌了。”莱顿说，“这毁掉了巢穴的一部分，但是树枝仍旧给它以支撑。”

　　But oddly enough, in these days of human-induced mass extinction, social weaver populations are actually on the rise. For that they can thank telephone poles, which they’re more than happy to use as artificial trees to build on.If that’s not a good call, I don’t know what is.

　　但奇怪的是，在人类干预生物大量消亡的背景下，群织雀的数量不降反增。这要感谢电线杆的存在——它们现在可以在此筑巢。如果这都不是个好兆头的话，我不知道还有什么是了。