Wed, Apr 10, 2019 - Page 14 News List

Highway gives way to purple crow butterfly swarms
紫斑蝶年度大遷徙 國道封閉讓路

A purple crow butterfly is pictured in Kaohsiung on Jan. 2.
紫斑蝶。一月二日攝於高雄。

Photo: Huang Chia-lin, Liberty Times
照片:自由時報記者黃佳琳

The mass migration of purple crow butterflies is one of Taiwan’s most spectacular ecological events. Numbers of migrating butterflies peaked at the end of last month, with a butterfly cascade of up to 1,200 insects per minute flying over National Highway No. 3 at Yunlin’s Linnei Township. This year has seen the largest purple crow butterfly migration recorded in a decade.

The purple crow butterfly and the monarch butterfly in Central and South America are the only two known butterfly species that engage in mass migrations. In Taiwan, the purple crow butterflies’ annual mass migration occurs from the wintering valleys in Kaohsiung and Taitung northward to their birthplace in areas such as Miaoli County. The returning butterflies will pass through Yunlin County’s Linnei Township en route, and butterfly watchers can most easily see them in the foothills of the mountains. The purple crow butterfly mass migrations mostly take place around Qingming Festival, otherwise known as Tomb Sweeping Festival, so purple crow butterflies are also known locally as Qingming butterflies.

The annual migration north crosses the Jhuoshuei River. One important section along its route is Section 252 of Highway No. 3. Nets are erected along a 2km stretch of this section, so that passing butterflies are not hit by speeding vehicles. Should the rate of butterflies exceed 250 per minute, the northbound outer lane will be closed.

On March 21, volunteers from the Taiwan Purple Crow Butterfly Ecological Preservation Association captured a small purple crow butterfly with its wing marked “MT217.” It had been marked and released in Kaohsiung’s Maolin District on Feb. 17, and taken 33 days to fly the 100 km to Linnei. It is believed the butterfly is headed to Miaoli’s Jhunan Township.

TODAY’S WORDS
今日單字

1. migration n.

遷徙

(qian1 xi3)

2. purple crow butterfly phr.

紫斑蝶

(zi3 ban1 die2)

3. peak v.

達到高峰

(da2 dao4 gao1 feng1)

4. monsoon n.

季風 (ji4 feng1)

5. honey plant phr.

蜜源植物

(mi4 yuan2 zhi2 wu4)


The purple crow butterfly migration occurs only when certain conditions are met. Firstly, the northeasterly monsoon needs to turn to a southerly wind, allowing the butterfly to ride the airflow northward. Secondly, the weather must be dry. Thirdly, there must be honey plants along the route. The last few years have brought challenges to the purple crow butterfly mass migration. Warmer weather and low rainfall, for example, have meant that there have been fewer honey plants, and they have bloomed at irregular times.

(Translated by Lin Lee-kai, Taipei Times)

紫斑蝶集體遷徙是台灣的生態奇觀之一,上月底達到最高峰,瞬間最大量每分鐘一千兩百隻飛越國道三號雲林林內段,形成一道壯觀蝶河,是十年來有紀錄的紫斑蝶遷徙最大量。

紫斑蝶與中南美洲帝王蝶是至今被發現唯二會集體遷徙的蝴蝶。在台灣,紫斑蝶每年春天從高雄、台東等地越冬蝶谷集體北返苗栗等北部出生地。雲林縣林內鄉是紫斑蝶返家必經之地,也是由山區進入平原最容易觀察的地方。因紫斑蝶大爆發時間大多在清明節前後,地方也將紫斑蝶稱為「清明蝶」。

紫斑蝶每年由南向北遷徙時,必須飛越濁水溪,其中國道三號二五二里路段是重要蝶道,為避免紫蝶飛越高速公路時被飛馳而過的車輛撞死,國道架設了長兩公里護網,只要紫斑蝶每分鐘飛越數達兩百五十隻以上,就會封閉北上外側車道。

台灣紫斑蝶生態保育協會義工三月二十一日捕捉到一隻翅膀標記「MT217」的小紫斑蝶。這隻小紫斑蝶於二月十七日在高雄茂林標放,花三十三天飛了一百公里抵達林內,預估將飛到苗栗竹南。

紫斑蝶遷移有其特定條件,需東北季風轉吹南風時,紫斑蝶才會乘著氣流,順風北上;第二,氣候必須乾燥,第三,還要有蜜源植物,這三個條件配合,紫斑蝶才會大量遷移。這幾年的暖冬現象,讓植物開花亂了套,加上雨量少,蜜源植物減少,紫斑蝶遷移面臨很大考驗。

(自由時報記者詹士弘、林國賢)

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