10-12 侯鸟具有更好的记忆力

Migrating Birds Remember Better

Migratory 1 birds not only get to see the world. A new study finds that these globetrotters also have better long-term memories than stay-at-home relatives. The extra brain power could help ensure that the birds don’t get lost on their travels.

Birds flying long distances use celestial 21 cues, their sense of smell, and Earth’s magnetic2 field as rough guides to navigation. As they are near their final destination, however, they switch strategies. They look for landmarks 3 such as bushes and trees they have memorized during previous trips. That's how the birds return to the same breeding, wintering, and stopover sites year after year. Anatomical3 studies suggested that migrants do a lot of learning en route4. Garden warblers5, for example, return to central Europe from their first trip to Africa with a bigger hippocampus6, a region of the brain involved in learning spatial 47 information. Nonmigrating Sardinian8 warblers, on the other hand, show no such change. But direct evidence that life on the move makes birds remember better was not found.

To investigate, scientists reared more than 100 nestling garden warblers and Sardinian warblers. In the fall, when the birds normally migrate, the scientists let each bird spend a few hours in two adjacent chambers 6, one decorated with fake geraniums9 and the other with fake ivy 7. More importantly from the birds' perspective, one of the chambers offered a supply of tasty dried insects and a pollen-sugar mixture. Whereas migratory garden warblers remembered the food-containing chamber 5 up to a year later, their sedentary relatives did so only for 2 weeks. It seems the migrating birds are somehow programmed to gather new information.

“It is hugely beneficial for migrants to remember where their territory is,” says Susan Healy, a biologist at University of Edinburgh, Scotland. “The new findings suggest that the garden warblers' bigger hippocampus gives them better long- term memory.” However, other scientists point out that the experiment doesn't show that the birds can remember specific landmarks they could use for navigation. It’s more like memory for habitat features.

注释：

1. celestial [si5lestjEl] a. 天的，天空的，天上的

2. magnetic [mA^5netik] a. 地磁的

3. anatomical [7AnE5tCmikEl] a. 解剖学的

4. en route [Rn5ru:t] ad. [法] 在途中

5. garden warbler [5wC:blE] [鸟] 园莺

6. hippocampus [7hipE5kAmpEs] n. [解] 海马（延伸于脑的每一个侧脑室下角底上的一条海马状突起）

7. spatial [5speiFEl] a. 空间的，与空间有关的，太空的

8. Sardinian [sB:5diniEn] a. 撒丁岛的，撒丁人的

9. geranium [dVi5reinjEm] n. 天竺葵属植物，天竺葵花

侯鸟具有更好的记忆力

候鸟并不只是四处观光。一项新研究发现，这些环球旅游者比起它们那些只呆在家中的亲戚们有着更出色、更持久的记忆力。它们超强的脑力确保它们在旅行中不迷失方向。

长距离飞行的鸟儿是靠空中标识、嗅觉以及地球磁场进行简单导航的。然而，当它们靠近目的地时便开始改变策略。它们找寻在前一次飞行中记住的地标，诸如灌木、树林等。这就是鸟儿如何年复一年地回到同一个繁殖地、过冬地和途经地的。解剖学研究表明，候鸟在迁徙过程中学到了很多本领。比如一种叫做园莺的鸟，先是飞到非洲，在返回中欧时，它们脑部的海马状突起，即大脑中涉及学习空间方位知识的组织，增大了。而非候鸟撒丁岛莺的大脑却没有这种变化。但是，迁移生活能使候鸟改善记忆力的直接证据却没有找到。

为了进行调查，科学家饲养了100多只园莺和撒丁岛莺的雏鸟。当候鸟通常迁徙的秋季来临时，科学家让每只鸟都在相邻的两个房间中呆几小时，其中一个房间用假天竺葵而另一个用假常青藤装饰。从鸟儿的角度来看，更重要的一点是，其中一间房子提供了可口的干虫以及花粉糖的混合物。一年以后，候鸟园莺还记得有食物的房子，可是它们不迁徙的亲戚却只过了两个星期便忘记了。候鸟就好像具有某种记忆新信息的程序似的。

“记住自己的领地对于候鸟来讲有着巨大的好处，”苏格兰爱丁堡大学的生物学家苏珊·希利这样讲道，“新的发现表明，园莺脑部较大的海马状突起使得它们有着更长久的记忆力。”但是其他科学家则指出，这项试验并不能表明候鸟能记住可以用来导航的特定地标。这更像是记住了栖息地的特征而已。