世界最大雀巢 你不知道的羣織雀

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.

非洲的羣織雀大概和麻雀一般大小。500只羣織雀聚居在一起，修建了世界上最大的窩巢——它重達2000磅，長20英尺，高7英尺。這個巢穴是如此的巨大，以至於它可以拖垮一棵大樹；而且修建精良可以留存一個世紀。巢穴裏大約有一百個房間，這大概是圍繞着一箇中心結構的脊椎結構的社會了——當然，除了人類和他們的摩天大樓。

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.

以半乾燥的納米比亞平原和南非爲家，羣織雀利用不同種類的材料，一個樹枝一個樹枝地織起它們的巢穴。一間間房裏鋪着奢華青草和羽毛，偶爾還有棉球出現。

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.

通常一間房裏會擠進3~4只羣織雀，而這時，這個巨大的建築的好處就相當明瞭了。冬夜總是凜冽的，在最寒冷的地方有時甚至會達到華氏20度。萊頓在鳥巢裏放置了一個熱式記錄儀，而後鳥兒入住了該巢穴。

“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.

“夜間的溫度大約是30~35華氏度，但是住着三四隻羣織雀的房間溫度可以達到70~75華氏度。”他說，“因此這些巢穴的保溫作用非常明顯。”而在炙熱的炎夏，房間依舊可以爲鳥兒提供舒適的環境。房間遠離巢頂，就意味着遠離了太陽而享受音量。而且房間像一個游泳池一樣把熱空氣隔離開，它會會在晚上儲存涼意以抵禦白天的熱量。

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.

特別待遇還不止這些。萊頓說，鳥兒把房間的門設在巢穴的底部，這樣它們也可以躲避老鷹的襲擊。而且也可以防止巢穴裏的洪澇。而且從進化的角度來看，羣居降低了它們被捕食的機會。

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.”

羣織雀的巢穴實在太可愛了，以至於吸引了不少其它的動物。非洲禿鷲喜歡把自己掛在屋檐上，紅頭雀會在房間裏養育子女——但有時它們會殺掉原本住在裏面的羣織雀。“有檔案記載，紅頭雀有時會吃掉羣織雀。”萊頓說，“雖然很不願意這樣說，但是羣織雀辛辛苦苦建造、維護它們的家，然而建成之後侵略者就席捲而來把它們吃掉。”

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，這並不意味着羣織雀不會奮起反抗。如果有蛇試圖爬上樹來，或者一隻紅頭雀逗留在屋頂，它們都會羣擁而出發出不停地發出高音警報。然而這可能會嚇跑小隻一些的鳥兒，卻趕不走紅頭雀和大蛇。

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給它們帶來危險。一些巢穴可能會留存數十年，因此在雨季會浸水變重，使得大樹無法承受它們的重量而倒塌。“就我研究的巢穴來看，最近一個夏天整棵樹都倒塌了。”萊頓說，“這毀掉了巢穴的一部分，但是樹枝仍舊給它以支撐。”

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 that’s not a good call, I don’t know what is.

但奇怪的是，在人類干預生物大量消亡的背景下，羣織雀的數量不降反增。這要感謝電線杆的存在——它們現在可以在此築巢。如果這都不是個好兆頭的話，我不知道還有什麼是了。