In their quest for perpetual flight, researchers at Lehigh University have taken note of the turkey vulture’s amazing ability to stay aloft indefinitely with very little effort, as it scans the terrain beneath it for carrion to feed on. In addition to gauging thermals and wind direction with their own sensors, it appears that turkey vultures closely monitor other birds of prey in the area and use the information gleaned from them to determine which areas would best support their effortless soaring. It is thought that they may even keep an eye on the movement of clouds and the swaying of trees to gather information about wind currents and thermals.
Also of interest to aviation researchers, is the turkey vulture’s unique ability to hold its wings in a shallow V-shaped angle for extended periods of time which allows it to stay aloft with little effort, as well as giving it the ability to use sidewinds to its advantage, converting them into speed and altitude at a moment’s notice.
The concept of ‘dynamic soaring’ was first described in the British journal Nature in 1883 by Lord Rayleigh in an article entitled The Soaring of Birds. There he states that a bird cannot maintain its level indefinitely, either in still air or in a uniform horizontal wind, without working his wings. He concluded that if a bird maintained his course for some time, without working his wings, the conclusion can be drawn that either: The course is not horizontal; the wind is not horizontal; or the wind is not uniform – the latter being the principle relating to dynamic soaring.
Turkey vultures, also known as turkey buzzards, or simply buzzards, have a wide range of habitat, being found from southern Canada right down to the southernmost point of South America. These large scavengers favor open and semi-open terrain where they can spot their next meal with ease, feeding almost exclusively on carrion. They roost in large groups, nesting in caves, thickets, or hollow trees. As they do not have a syrinx, they can only make grunting and hissing noises. Legally protected in the United States, and with very few natural predators, turkey vultures have an IUCN conservation status of ‘least concern’.
Various methods of marking birds for identification are believed to go back as far as Roman times and this was generally done to indicate ownership. The first person to ring birds for scientific purposes was Danish ornithologist Hans Christian Cornelius Mortensen (1856-1921) who put aluminum rings marked with unique numbers and an address, first on the legs of European Starlings, and later on storks, herons, gulls and ducks, with the intention of tracking their movements. The first organized banding scheme was established at the Rossitten Bird Observatory by German ornithologist Johannes Thienemann in 1903.
Since those early days bird banding has been invaluable in gathering data for conservation and scientific purposes. But banding has its limitations, as once birds are set free they are very often only identified again when found injured or dead, and then only if the person finding the bird takes the time and trouble to report it. At best, bird banding provides only a few pieces of the puzzle of bird migration and behavior. However, rapidly advancing technology has opened up new avenues of tracking birds, with the most promising being satellite telemetry, which provides information immediately.
In 2005, satellite telemetry was used by the Wildlife Research Institute (WRI) and the United States Forest Service (USFS) to track Southern California’s Golden Eagles, and this was later expanded to include Montana. Tiny transmitters are attached to the birds and their signals are tracked by satellites no matter where they may travel. Working in conjunction with the National Oceanic and Atmospheric Administration (NOAA) the WRI received data via the internet enabling researchers to determine exactly where the eagles have been and when. The information is so detailed that it can be determined how high the eagles flew, and how fast they were flying. In the event of an eagle not moving, it’s location can be pinpointed and the bird rescued if injured, or recovered if dead.
As plans for alternative energy sources in the form of wind and solar farms move ahead in California, data on migration, nesting and hunting patterns of Golden Eagles will be invaluable in ensuring the survival of this already endangered species. On a wider scale, the cost and availability of satellite telemetry is an obstacle that may be difficult to overcome, particularly in developing nations, and so bird banding remains an important activity for conservationists.