2. 迁徙飞行的高度
鸟类迁徙时的飞行高度一般在1000 m以下，小型鸣禽的高度不超过300 m，大型鸟类的高度可达到3000-6300 m之间。曾经有记录天鹅飞越了珠穆朗玛峰。 在墨西哥海湾，曾经有人研究过鸟类在夜间和白天迁徙高度的区别，夜间迁徙的高度在244-488 m，白天的迁徙高度则在 1220-1524 m之间。 天气也影响鸟类迁徙的高度，晴朗时鸟类飞行较高，有云雾和强劲的逆风时，鸟类则低空飞行。

二、对信鸽飞行的观察
笔者通过多年细致观察归巢途中的信鸽发现，大部分信鸽在飞行途中靠不断扇动翅膀保持较低的飞行高度（50米左右）向前飞行；而个别信鸽呈忽高（300米以上）忽低（30米左右）的波浪式飞行，且这些信鸽通常单飞于鸽群的前列，飞行速度较快。

Most birds fly below 500 feet except during migration. There is no reason to expend the energy to go higher -- and there may be dangers, such as exposure to higher winds or to the sharp vision of hawks. When migrating, however, birds often do climb to relatively great heights, possibly to avoid dehydration in the warmer air near the ground. Migrating birds in the Caribbean are mostly observed around 10,000 feet, although some are found half and some twice that high. Generally long-distance migrants seem to start out at about 5,000 feet and then progressively climb to around 20,000 feet. Just like jet aircraft, the optimum cruise altitude of migrants increases as their "fuel" is used up and their weight declines. Vultures sometimes rise over 10,000 feet in order to scan larger areas for food (and to watch the behavior of distant vultures for clues to the location of a feast). Perhaps the most impressive altitude record is that of a flock of Whooper Swans which was seen on radar arriving over Northern Ireland on migration and was visually identified by an airline pilot at 29,000 feet. Birds can fly at altitudes that would be impossible for bats, since bird lungs can extract a larger fraction of oxygen from the air than can mammal lungs.

Other high flying birds include whooper swans, once observed by a pilot at 27,000 feet over the Atlantic between Iceland and Europe, and bar-tailed godwits (a shorebird), which have been seen at almost 20,000 feet. The record for North America is a mallard duck that collided with an airplane at 21,000 feet above Elko, Nevada in July, 1963. Most birds, though, fly lower--waterfowl typically at between 200-4,000 feet, and small songbirds at between 500-2,000 feet. However, the tiny Blackpoll warbler will fly up to 16,000 feet high in order to catch favorable winds on migration between Canada and South America. I'm not sure how well a sparrow would do, but similar-sized birds are quite capable of flying very high indeed.

4楼: Originally posted by 7144 at 2012-12-25 13:01:51
现存鸟类9000余种，你老师让你们研究哪种？
针对性研究应该比较容易找。耐心找找，好好做作业。




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