What exactly determines the speed at which birds fly? Is it simply the mass of the bird? Does it have something to do with their wings span? Actually it is somewhat more complicated than that.
A group of Swedish scientists has researched one hundred thirty eight species of birds. The team of researchers analyzed flight patterns of all of these birds. Through this research they were able to determine that flight speed is not just determined by size but also has do with lineage of the species.
In their study the researchers collected cruising speeds of many species of migratory birds. The total is representative of about thirty three percent of all European bird species.
At first guess, most would argue that larger birds, especially those with large wingspan would have the fastest speed. But as the researchers found, this is not always an indicator of the speed at which birds will fly. A great deal of a species flight speed is attributed to their history throughout evolution. So, for example, birds of prey, because of their size and wing span had slower speeds than say, songbirds.
One very interesting bird is the Swift. It is primarily found in Africa and Europe. These birds do not land to rest but remain above ground. Their optimal speed for this gliding is 8 meters per second. At this speed they are able to glide more which means flapping their wings less, thus saving energy.
Although this study is just an indicator of flight speed, there will be many more studies to come. The study suggest that there are different types of adaptions that have been made through the centuries by different bird species. However, there is still much more to be explored on this fascinating topics.