Monday, March 29, 2010

Bird Flight & Height

By Susan Benson,
CNHM Director of Education

While recently talking with some girlfriends, we got on the topic of our experiences speeding along area roads in our cars. Some interesting stories were told. The next morning I was watching a flock of robins migrating through my yard, and started wondering about their speed. How fast do they fly? How high do they fly? Certainly the science of flight speeds in the bird world must be imprecise given that birds deal with head or tail winds, or barometric pressure. Does bird age affect their flight? How can we tell if a bird is flying at its top speed, or is just cruising along? What estimates exist on flight speed and altitudes was a question I wanted to answer.

A robin has been measured at 30 mph, while an arctic loon can fly at 56 mph, the common loon at 90, and the killdeer and wood duck at 55 mph. A canvasback duck can reach 72 mph, and a tiny hummingbird has been “clocked” at 27 mph, but at 50 mph with a tail wind. This top speed, by the way, rivals a Canada goose – apparently size is not an indicator of speed!

Bird air speed has been estimated from cars and planes. Doppler radar, the device similar to that which police use to catch speeders, has been used to measure ground speed of birds. Alternatively, using wind speed measurements with an anemometer, scientists have estimated bird airspeeds. These measurements were also calculated with power requirements. For example, there is a top speed with which a bird can fly, and the speed with which it usually does fly. Birds appear to minimize their energy use, or metabolic rate, and maximize the distance they can travel during the time in which they expend their energy. A bald eagle that is searching for prey may minimize their energy expenditure by soaring while using a thermal, or bubble of warm air. A bird might also choose its maximum speed when in flight from a predator. These studies found that a gull can fly 15 to 28 miles per hour (mph) without raising its metabolic rate more than 15 percent. Some bird species that have a courtship flight reach their maximum speeds during these flights. Small woodland birds fly faster in open areas, while birds in flocks fly faster than when flying alone. During a chase, a duck can reach up to sixty mph, while a peregrine falcon can reach 200 mph. That is fast!

How high do birds fly? Birds have been spotted on the top of Mount Everest, at more than 29,000 feet, and in the Himalayas at 25,000 feet. Even the smallest warbler has been seen flying at an altitude of 9,000 feet, a real feat since breathing at high altitudes, mixed with cold air can make flight challenging. On the flip side, the emperor penguin has been recorded swimming at an ocean depth of 875 feet.

Most birds fly below 500 feet except during migration. Long-distance migrants have been observed flying at 5,000-20,000 feet. Whooper swans were observed by a pilot at 29,000 feet. This is amazing considering the air at 20,000 feet has less than half the oxygen at lower levels. Vultures will rise to over 10,000 feet, presumably to scan larger areas for food, and to observe where other vultures are feeding. Radar observations have shown that nocturnal migrants fly higher as well. Scientists believe that this might make for better tail winds, and cooler air decreases water loss due to evaporation and allows migrants to regulate their body temperature with greater ease. Landmarks might be easier to locate from up high. The birds also do not have to do battle with fog, clouds, or other physical barriers. On the other hand, some water birds and land birds have been observed migrating low over the water, rarely rising above 200 feet. What amazing diversity birds can show!

We often hear stories of birds flying “a mile a minute,” and although we know that most birds do not reach that accelerated speed for long, we can certainly appreciate their abilities. As I sometimes fly around “a mile a minute” in my own personal life, nature and birds can be a reminder to slow life down for a moment, or two, or two thousand, giving us time to enjoy the beauty around us.

For over 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility and new exhibit, Our Shared Planet, in Cable at 13470 County Highway M. Also find us on the web at to learn more about our exhibits and programs. Post your own stories on the Nature Watch blog at

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