評論
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Science and Technology Mimicry The first sparrowhawk of spring
科技 模仿 春天第一只雀鷹
To obtain better access to warbler nests, cuckoos mimic raptors
為了更好地搶占鶯的巢穴，杜鵑通常會模仿成猛禽的樣子
THE resemblance between cuckoos and sparrowhawks has been a cause of comment since ancient times.
杜鵑和雀鷹之間的相似性自古以來就是引發評論的原因。
As the photographs above show, the two birds (cuckoo on the left, sparrowhawk on the right) are similar in size, shape and plumage, and both have a conspicuous pattern of bars on their breasts—a pattern found on many species of hawk, but not on the cuckoo's relatives.
正如上面的照片顯示的兩只鳥（左側的是杜鵑，右側的是雀鷹），它們在大小，形狀和羽毛上都很相似，二者的胸前都有突出的條紋——許多鷹類都有這種類型的條紋，但杜鵑的親戚中卻沒有。
Until now, though, no one has thought to take that observation any further, and test whether the one is truly mimicking the other.
雖然現在還沒有人對此進行更深入的觀察，并證實杜鵑是否真的在模仿對方。
Cuckoos would have good reason to do so, since the warblers and other small birds in whose nests they lay their eggs are understandably frightened of hawks, and give them a wide berth.
杜鵑有很好的理由去模仿鷹，由于鶯和其它的小型鳥類在它們的巢中產卵，自然這些小型鳥類就很害怕鷹，并且對鷹敬而遠之。
Such leeway would make it easier for a female cuckoo to lay where she chose.
這樣的空當就給了雌杜鵑自由選擇巢穴產卵的機會。
Nick Davies and Justin Welbergen, a pair of ornithologists at Cambridge University, have now corrected that omission.
尼克?戴維斯(Nick Davies)賈斯汀?韋伯爾根(Justin Welbergen)是劍橋大學的鳥類學專家，它們現在補充了這種遺漏。
They have tested the idea that cuckoos mimic hawks—or, at least, that warblers think cuckoos look hawklike.
它們已經證實了杜鵑會模仿鷹——或者說，至少在鶯看來，杜鵑非常像鷹。
As they report in the latest edition of Behavioral Ecology, they have found that it is true, but only up to a point.
就像它們在最新一期的Behavioral Ecology上報道的那樣，它們已經發現這是正確的，但至少在某種程度上可以這么講。
To carry out their test, Dr Davies and Dr Welbergen put stuffed birds near reed-warbler nests, to observe the nestholders' reactions.
為了進行它們的測試，戴維斯博士和韋伯爾根博士將幾種鳥類標本放到了鶯的蘆葦巢附近，用來觀察這些巢主人的反應。
They used three species: sparrowhawks (which are a direct threat to a warbler's life), cuckoos (which do not harm adult warblers, but do stop them reproducing successfully) and doves (included as a control, since they pose no threat at all).
他們用了三種鳥類：雀鷹（直接威脅鶯生命的猛禽），杜鵑（不會威脅成年鶯類，但是會順利地影響鶯類的繁殖），還有鴿子（只是作為一個對照，它們不會對鶯類造成任何威脅）。
The breast of each stuffed bird was adorned with a piece of white silk.
每種鳥類的胸前都用一塊白色的絲綢裝飾。
Some pieces of silk were left plain. Others had bars drawn on them with a felt-tip pen.
一些絲綢偏左放置。其它條紋則用記號筆畫制而成。
Once the stuffed birds were in place, the two researchers recorded the reactions of the nestholders.
一旦將這些鳥類標本放置好，這兩位研究人員就記錄巢主人的反應。
In particular, they measured how closely the nestholders were willing to approach the stuffed intruder, and also how noisily the intruder was mobbed, in an attempt to drive it away.
他們會專門評估這些巢主人對于不速之客的接近程度，以及圍攻入侵者并試圖將其趕走的激烈場景。
The barring, they found, was crucial.
他們發現了一個非常關鍵的例外。
Though the warblers could clearly tell the difference between the species (they mobbed the cuckoos most and stayed farthest away from the sparrowhawks),
雖然鶯類可以很清楚地分辨出這些鳥類的不同（它們主要圍攻杜鵑，最大限度地遠離雀鷹），
in the cases of all three types of stuffed bird those decorated with stripes were approached more cautiously and mobbed less than those without stripes.
對于那些裝飾了條紋的三種鳥類標本，它們更謹慎地接觸，并且圍攻那些沒有條紋的鳥類。
Hawk-like stripes do, then, provoke what is, from a cuckoo's point of view, the desired reaction:
從杜鵑的角度來看，鷹狀條紋所起的主要作用就是它所希望看到的：
less of the sort of behaviour that is likely to interfere with her egg-laying mission.
如果缺乏這種行為會則會影響到杜鵑的產卵任務。
Not perfect mimicry, but good enough to be useful.
雖然這種模仿不甚高明，但已經足夠用了。
Probably, Dr Davies and Dr Welbergen have caught cuckoo and warbler in the middle of an evolutionary arms race.
也許戴維斯博士和韋伯爾根博士已經注意到了杜鵑和鶯正處于一個進化的軍備競賽中。
Come back in 10,000 years and cuckoos and sparrowhawks may be indistinguishable.
回到10000年前，杜鵑和雀鷹或許就難以分辨了。
