![]() Given the role we know dispersal plays in evolutionary processes, from speciation to species interactions, we suspect this relationship between behaviour, the environment, and dispersal may be shaping other aspects of biodiversity."Įxamples of fundamental patterns potentially explained by variation in dispersal include the smaller geographical ranges noted in tropical species.ĭr Joseph Tobias, senior author of the study, based at Imperial College London, added: "We hope our measures of wing shape for over 10,000 bird species will have numerous practical applications, particularly in ecology and conservation biology, where so many important processes are regulated by dispersal. A comparison of bird wings and bat wings is an example of both homology and analogy. (Incidentally, the word alula is Latin for 'little wing.' 'Little Wing' is also the name of a classic song by Jimi Hendrix.). The study's lead author, Dr Catherine Sheard from the University of Bristol's School of Earth Sciences, said: "This geographic pattern is really striking. The alula bone supports a few feathers that can be moved separately from the others on the wing. New research published today in Nature Communications has analysed this index for over 10,000 species of birds, providing the first comprehensive study of a dispersal-linked trait across an entire class of animals.Ī global team of researchers, led by the University of Bristol and Imperial College London, measured the wings of 45,801 birds in museums and field sites around the world.įrom these, the team created a map of the global variation in wing shape, showing that the best-adapted fliers were primarily found in high latitudes while birds adapted to more sedentary lifestyles were generally found in the tropics.īy analysing these values along the bird family tree, together with detailed information about each species' environment, ecology, and behaviour, the authors found that this geographical gradient is primarily driven by three key variables: temperature variability, territory defence, and migration. Measurements of wing shape - particularly a metric called the 'hand wing index', which reflects the elongation of the wing - can quantify how well the wing is adapted for long-distance flight and is easily measured from museum specimens. The good news is that bird wings offer a clue. Yet since tracking animal movement is difficult and expensive, there are still huge gaps in knowledge about animal movements and dispersal, particularly in more remote parts of the world. The way different organisms vary in how much they move around is a key factor in understanding and conserving biodiversity. A small projection on the leading edge of a bird’s wing, the alula, or bastard wing, is a Bird’s thumb, used to facilitate flight, landing, & maneuverability at low-speed. Middle primary covert: mid-sized feathers covering the wing. Alula: feathers of the leading edge of the wing, attached to the thumb bone. Down fethers: small feathers of the wing. Middle covert: mid-sized feathers of the wing. The Arctic tern flies from the Arctic to the Antarctic and back again each year, while the Inaccessible Island rail - the world's smallest flightless bird - never leaves its five-square-mile island. Wing of a bird: a warm-blooded animal with two wings, two feet, a horny beak and a body covered with feathers.
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