ScienceFocus (issue 009) - page 13

located far out of reach within the trunks of trees
and far above the ground. To reward the bird, the
Yao people leave behind wax ceremonially on a
bed of leaves. After all, the birds have earned it;
with a honeyguide’s help, honey hunters are able
to triple the chance of locating hives [2].
Initial Western reports of this phenomenon
appeared in the 16th century, when a Portuguese
missionary noted that a small bird pecked at the
candlesticks in his church and could guide seekers
to beehives. For centuries, it had been dismissed as
myth, until the 1980s when Isack and Reyer showed
that the Boran people of Kenya were purposefully
following the honeyguide. Unlike the Yao, the
Boran summoned honeyguides with sharp whistle-
like sounds. With the help of the honeyguide, the
Boran are able to cut down search time from nine
hours to three [3].
The mutualistic behaviour – describing two
parties both benefitting from a shared relationship
– is frequently observed in the natural world. Plants
and pollinators depend on each other, as do
gut bacteria and humans. The Hadza people of
Tanzania also follow honeyguides to locate honey,
but their relationship moves from a mutualistic one
to a manipulative one, where one party acts in
a way that is beneficial to them but costly to the
other party [5]. The Hadza people manipulate
honeyguides by destroying the wax that they
非洲撒哈拉沙漠以南的森林中常見的黑喉響蜜鴷
(拉丁學名:
Indicator indicator
),是能夠消化蜂蠟的少數
鳥類之一。牠們還會進食蜂窩內的其他東西,如:蜂卵、幼蟲
和蜂蛹等 [1],所以特別擅於尋找蜂窩。不過,對於這些手無
寸鐵的小鳥來說,要躲避蜂蜇是有一定的難度,要借助於莫
桑比克北部的堯族採蜜人。
採蜜人以嘹亮的顫音
呼嚕聲,召喚附近的響蜜鴷。響
蜜鴷會報以鳴聲並飛向蜂窩。在唱和聲中,人鳥重複互認,
尋找共同目標。一旦發現蜂窩,採蜜人會以煙火包圍蜂窩,讓
蜜蜂無法分辨進攻源頭,然後破開蜂窩取走蜂蜜。整個過程
一點都不簡單,因為蜂窩往往位於不能觸及的樹幹之內或高
處。堯族人會特意在一堆樹葉上留下蜂蠟,作爲對小鳥的獎
勵。畢竟,這是響蜜鴷應得的酬金。在牠們幫助之下,採蜜人
找到蜂窩的機會是平常的三倍 [2]。
最早關於這現象的西方報導,出現在16世紀。當時一位
葡萄牙傳教士,記錄了有一隻小鳥啄食他教堂內的蠟燭,還
find – burning, bur ying or hiding, to
deliberately deprive honeyguides of their
reward. According to Hadza tradition, this
behaviour keeps honeyguides hungry and
motivated to find more hives.
Even with the promise of reward, the
origin of honey guiding is called into question.
The birds are not trained or domesticated, and
are wild by every definition. Yet, they voluntarily
engage with humans to establish a mutualistic
relationship. Honeyguides themselves, however,
are guilty of their own manipulative behaviour
toward other birds. In fact, they are oftentimes
referred to as ‘African cuckoos’ for its cuckoo-
esque parasitism. Female honeyguides are unable
to build their own nests and thus, sneak into the
underground nests of bee-eating birds, pierce the
host’s eggs and supplant their own eggs in the
nest. The host bird is often unaware of the switch,
and obliviously incubates the new clutch [5].
Competition between female honeyguides
is also fierce; around one third of parasitised
nests contain eggs from two or more females
and bee-eater hosts are only able to provide
so many insects. To gain the evolutionary edge,
honeyguide eggs ver y much resemble host
eggs in size. Unlike in the case of the cuckoo
bird, however, the honeyguide’s mimicry aims
to fool other honeyguides instead of the host.
為尋找蜂窩者引路。幾個世紀以來,人們視之為神話。直到
80年代,Isack 和 Reyer 證實肯尼亞的波拉納人故意跟隨
響蜜鴷。不過,波拉納人使用的叫聲像口哨般較為尖銳。有
了小鳥的幫助,波拉納人就能把搜索時間由9小時減至3小時
[3]。
這種雙方都能受益的互惠行為在自然界中甚為普遍,例
如:植物和傳粉者彼此依賴,腸道細菌和人類亦如是。坦桑尼
亞的哈紮人也會跟蹤響蜜鴷尋找蜂窩,不過兩者的關係從互
惠變成了操控,以致一方得益而另一方受損 [5]。哈紮人的操
控手段是銷毀、掩埋或者隱匿找到的蜂蠟,故意剝削響蜜鴷
的酬勞。按照哈紮傳統,這種行為是要讓響蜜鴷飢餓,廹使牠
們尋找更多的蜂窩。
雖然可以得到獎勵,這種「導蜜」行為的起源還是讓人費
解。響蜜鴷既沒有經過培訓亦不是家養,肯定是野生動物;卻
自願地與人類建立互惠的關係。不過響蜜鴷本身,也會對其
他鳥類作出操縱行為。
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