Nonstop for 7,000 miles
These Bird Species are Uniquely Adapted For Long Distance Travel
by Hailey Alfred, age 18
Bar-tailed godwits, bristled-thighed curlews, and artic terns are three examples of birds that make amazing migrations. They travel thousands of miles over vast expanses of ocean in one big stretch. It may seem an impossible feat, but through millions of years of evolution these various bird species have adapted well for their long journeys.
For example, the bar-tailed godwit and other long-distance migrators bulk up before their flight by consuming mass quantities of food. While eating, the birds’ liver and intestines enlarge so they are able to hold even more food. They then digest the food as fast as possible, allowing them to build large breast muscles and convert the excess food to fat.
When the birds are ready to migrate, their bodies are 55 percent fat. As the birds fly, they use this fat as a source of energy, eliminating the need to stop for food along the way. This method allows the bar-tailed godwit to fly continuously for 7,200 miles. It takes them nine days to migrate from Alaska to New Zealand.
Scientists study long-distance migrators using small transmitters known as geolocaters. Researchers soon discovered that some birds, such as the artic tern, were unable to carry the transmitters because they were too heavy. The solution: scientists developed even smaller transmitters.
Geolocaters weighing as little as one-twentieth of an ounce are now available. Transmitters this small, however, are unable to communicate with satellites and can only record light levels. Once the birds have completed their migration, scientists must recapture the birds with transmitters to extract data. Using computer software, researchers can determine where the birds traveled according to the rising and setting of the sun.
Long and short-distance migrators are genetically very similar. In fact, it’s possible that short-distance migrators could actually push themselves to perform the vast trips of long-distance migrators but choose not to because the risk of this dangerous journey outweighs its benefits. Traveling such long distances takes tremendous effort, and thus makes the birds more vulnerable to predators.
The bar-tailed godwit, however, has discovered a safe way to travel these long distances. They travel over the ocean to reduce encounters with predators. They also travel to areas such as New Zealand, where there are fewer predators, allowing them to rest after their long journey.
Scientists are baffled by the abilities of these birds because they travel such long distances and because they navigate so well. It is not as if the birds are fitted with their own GPS systems, yet somehow they know exactly where to fly.
Some of these species are known to use Earth’s magnetic field. Scientists now believe that the birds use a combination of navigation tricks to make their long trips, but they do not completely understand how it all works. The birds’ ability to navigate these long distances remains largely a mystery.
[Sources: The New York Times; Simpson Street Free Press]