Early Birds Miss the Worms(早出生的小鸟会没有毛毛虫可吃）_生物论文

　　抚养后代需要花费很多的时间，耗费很多的能量。对于生物来说，如果没有足够的食物是一件非常危险的事情。经过长期的研究发现：如果大自然不合作的话，亲代对后代的抚养可能会成为空话。这片文章中揭示：全球气候变暖可能会导致某些鸟类灭绝，因为在食物丰富，可以养活后代之前，这些鸟已经结束了抚养后代的任务。

Climate casualties. Changing climates may cause blue tits to breed out of sync withtheir food source.
CREDIT: GEORGE MCCARTHY/CORBIS

　　自从80年代，法国蒙彼利埃市功能和进化生态研究中心的进化生态学家Jacques Blondel 就开始研究生活在橡树林中的一种叫做蓝山雀的小鸟。他选择了两个研究地点，一个是在他的研究所附近的树林中，另一个是在125公里外的科西嘉岛上。在这两个地方，蓝山雀选择不同的生境作为繁殖场所。在科西嘉岛上，小山雀选择常绿的橡树林作为繁殖地，而在蒙彼利埃市小山雀则选择落叶的橡树林作为繁殖场所。然而，现在仍有很多生活在大陆上的鸟类，都像生活在科西嘉岛上的山雀一样，选择常绿橡树林筑巢。

　　大约在四年前，Blondel 和Donald Thomas （加拿大的生理生态学家）决定进一步追踪小山雀的鸟的活动情况。研究发现：如果让蒙彼利埃市的山雀在常绿橡树林中抚养后代，那它需要的能量是科西嘉岛上山雀抚养后代所需能量的两倍。

　　原因是：蒙彼利埃市的小鸟繁殖的时间不合适。Thomas说：科西嘉岛上的蓝山雀在六月份繁殖，这只正是新叶刚刚长出来的时候，而嚼食树叶的毛毛虫的数量也是最多的。在大陆上，大多数的鸟类要比科西嘉岛上的山雀提早3个星期繁殖，因为在大陆，落叶橡树发芽的时间较早，所以毛毛虫数量丰富的时间也比较早。如果让大陆的山雀到常绿橡树林中去筑巢的话是非常不利的。因为这些橡树仍然没有发芽，在五月份毛毛虫也还没有出现。没有充足的食物来源，这些鸟也就不得不提早地结束它们抚养后代的工作。而且这还会耗费小鸟体内储存的脂肪，当冬天来临的时候，这些鸟很容易因饥饿而死亡。

　　荷兰生态研究所的Marcel Visser说：这项研究证实了提早繁殖是需要代价的。气候条件和季节交替时间的改变，会使得越来越多的鸟变得不再适应繁殖。

原文：

　　Raising young takes time and burns energy. There‘s alsothe risk that a creature won’t have enough food for itself or its young. Now along-term study published in the 30 March issue of Science confirmsthe toll that breeding can take if nature doesn‘t cooperate. The paper suggeststhat global warming may catch some birds in a race against time, because theymay end up breeding before food is plentiful.

　　Eachspring since the 1970s, evolutionary ecologist Jacques Blondel of the Center ofFunctional and Evolutionary Ecology in Montpellier, France, has studied smallbirds called blue tits in the woods near his institute and in Corsica, anisland 125 kilometers away. Typically, blue tits in the two locales breed indifferent habitats--evergreen oak trees in Corsica, and deciduous oaks aroundMontpellier. Yet some of the continental birds were atypical and nested inlocal evergreen oak forests, just like the ones in Corsica.

　　Fouryears ago, Blondel and Donald Thomas, a physiological ecologist at the Universityof Sherbrooke in Quebec, Canada, decided to look more closely at these odd onesout. By injecting isotopes, the researchers learned that the Montpellier birdsbreeding in evergreen oak forests use almost twice as much energy in rearingtheir young as the birds in Corsica do. The birds hopped about at a rate thatthey can’t sustain for long.

　　Thereason: bad timing on the part of the Montpellier birds, Thomas says. TheCorsica blue tits breed in June, right when new leaves come out andleaf-munching caterpillars are most abundant. On the continent, most birdsbreed 3 weeks earlier, coinciding with the greening of the deciduous oaks and,again, an abundance of caterpillars. That puts the atypical population nestingin evergreen oaks near Montpellier at a disadvantage: Those trees are notbudding, and caterpillars have not yet emerged in May. Out of sync with theirfood source, those birds end up having to work much harder. That may burn fatreserves, leaving the birds more vulnerable to starvation during the winter,Thomas suggests.

　　The newwork "confirms what many people thought but were never able to show: thatbreeding too early has a fitness cost," says Marcel Visser of theNetherlands Institute of Ecology in Heteren. Thus, the work hints that as climatechanges and the timing of the seasons shifts, says Blondel, "more and morepopulations of birds will become maladapted to breeding."

摘自：

http://sciencenow.sciencemag.org