Sun, Dec 15, 2019 - Page 9 News List

Bye-bye, birdie: Study finds North American birds getting smaller
生態警訊 北美洲鳥類體型逐年縮水

Ledgers recording body size measurements, measuring tools and a Tennessee Warbler are pictured in this photo released on Dec. 4.
這張十二月四日發布的照片中,紀錄本上記載著鳥類體型尺寸,旁邊擺著測量工具,以及一隻田納西林鶯。

Photo: Reuters
照片:路透

Since 1978, researchers have scooped up and measured tens of thousands of birds that died after crashing into buildings in Chicago during spring and fall migrations. Their work has documented what might be called the incredible shrinking bird. A study published on Dec. 4 involving 70,716 birds killed from 1978 through 2016 in such collisions in the third-largest US city found that their average body sizes steadily declined over that time, though their wingspans increased.

The results suggest that a warming climate is driving down the size of certain bird species in North America and perhaps around the world, the researchers said. They cited a phenomenon called Bergmann’s rule, in which individuals within a species tend to be smaller in warmer regions and larger in colder regions, as reason to believe that species may become smaller over time as temperatures rise.

The study focused on 52 species — mostly songbirds dominated by various sparrows, warblers and thrushes — that breed in cold regions of North America and spend their winters in locations south of Chicago. The researchers measured and weighed a parade of birds that crashed into building windows and went splat onto the ground. Over the four decades, body size decreased in all 52 species. The average body mass fell by 2.6 percent. Leg bone length dropped by 2.4 percent. The wingspans increased by 1.3 percent, possibly to enable the species to continue to make long migrations even with smaller bodies.

“In other words, climate change seems to be changing both the size and shape of these species,” said biologist Brian Weeks of the University of Michigan’s School for Environment and Sustainability, lead author of the study published in the journal Ecology Letters. “Virtually everyone agrees that the climate is warming, but examples of just how that is affecting the natural world are only now coming to light,” added Dave Willard, collections manager emeritus at the Field Museum in Chicago who measured all the birds.

TODAY’S WORDS
今日單字

1. scoop v.

鏟起、撿拾

(chan2 qi3, jian3 shi2)

2. migration n.

遷徙

(qian1 xi3)

3. wingspan n.

翼展

(yi4 zhan3)

4. phenomenon n.

現象

(xian4 xiang4)

5. songbird n.

鳴禽

(ming2 qin2)

6. unprecedented adj.

空前的、前所未見的

(kong1 qian2 de5, qian2 suo3 wei4 jian4 de5)


The study provides fresh evidence of worrisome trends for North American birds. A study published in September documented a 29 percent avian population drop in the US and Canada since 1970 and a net loss of about 2.9 billion birds. “I think the message to take away is this,” Weeks said. “As humans change the world at an unprecedented rate and scale, there are likely widespread and consistent biotic responses to environmental change.”

(Reuters)

自一九七八年起,研究人員撿拾並測量了數萬隻在春季及秋季遷徙期間,因為撞上芝加哥的建築物而死亡的鳥類。該研究記錄到鳥類體型不斷縮小,變化程度讓人難以置信。這份研究發表於十二月四日,研究對象為一九七八年至二○一六年間,在美國第三大城芝加哥死於這類撞擊的七萬零七百一十六隻鳥兒。研究發現,雖然這些鳥兒的翼展長度增加,平均體型卻在這段期間逐年縮水。

研究人員表示,這項結果顯示持續暖化的氣候正在急速壓縮北美洲特定鳥種的體型,類似的情況或許也發生在世界各地。研究人員引述伯格曼法則──單一物種的個體在較溫暖地區體型通常較小,在較寒冷的地區體型通常較大──的現象作為理論根據,指出物種體型可能會隨著氣溫升高而逐漸變小。

該研究聚焦於五十二種鳥類──大多數是各種麻雀、林鶯以及畫眉鳥為主的鳴禽,它們在北美的寒冷地區繁殖,冬天則遷徙到芝加哥南方的地區度冬。研究人員對一連串撞上建築物窗戶、隨後墜落在地面上的鳥類進行測量與秤重。結果發現,過去四十年來,五十二種鳥類的體型全部都縮小了:平均身體質量減少了百分之二點六,腿骨長度縮短了百分之二點四。然而,翼展則增加了百分之一點三,可能是為了讓這些物種能夠以較小的體型繼續進行長途遷徙。

密西根大學環境與永續學院的生物學家布萊恩‧韋克斯指出:「換言之,氣候變遷似乎正在改變這些物種的體型大小和外觀。」這份研究發表於《生態學通訊》期刊,威克斯為主要作者。芝加哥費爾德博物館的榮譽館藏管理員戴夫‧威拉德,在這篇研究中負責測量所有鳥類,他進一步補充說:「幾乎所有人都同意氣候正在暖化,但是它到底如何影響自然界,這方面的實例現在才開始浮上檯面。」

這份研究為北美洲鳥類族群多項讓人憂心的趨勢提供新的證據。今年九月發表的一份研究,記錄到美國和加拿大自一九七○年以來鳥類數量減少了百分之二十九,淨損失多達二十九億隻鳥兒。韋克斯說:「我想,我們從中得到的訊息是──當人類以空前的速率和規模改變地球,可能就會造成廣泛且持續發生的生物反應,以回應環境的變遷。」

(台北時報章厚明譯)

Comments will be moderated. Keep comments relevant to the article. Remarks containing abusive and obscene language, personal attacks of any kind or promotion will be removed and the user banned. Final decision will be at the discretion of the Taipei Times.

TOP top