The shape of its wing can provide clues as to which birds are long-distance travellers and which ones are short-range fliers, according to research.
Analysis of 10,000 avian species has shown birds living in high-latitude areas are better equipped for long-haul flights than their tropical cousins living near the equator.
The researchers believe birds’ wings may have adapted to the environment and behaviour of the species, meaning not all creatures are able to fly long distances unless their wings have specifically evolved for this feat.
They said it is the reason why the Arctic tern is able make round trips between Arctic and the Antarctic while the Inaccessible Island rail, which is the world’s smallest flightless bird, never leaves its home in the Pacific Ocean.
The scientists believe their findings, published in the journal Nature Communications, could help understand species dispersal across “an entire class of animals”.
Dispersal, which is the movement of species from one place to another, plays a key role in the ecological process and is crucial for maintaining healthy ecosystems and biodiversity.
Understanding more about this process could help biologists gain insight into how new species are formed (speciation) and why some species go extinct.
A 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.
They used a metric known as the hand-wing index (HWI), which is a measure of the elongation of the wing, to determine which types of wings are adapted for long-distance flight.
Previous research has shown birds with shorter and more rounded wings are less likely to travel long distances than their counterparts with long pointy wings.
Based on the HWI measurements, the team was able to create a “map” of birds and their different wing shapes.
Three key factors – temperature variability, territory defence and migration – were found to play a role in how well birds’ wings adapted for long-haul flights.
According to the researchers, their findings indicate HWI “is correlated with geography and ecology across 10,391 bird species, increasing at higher latitudes and in migratory and/or non-territorial species.”
Dr Catherine Sheard, from the University of Bristol’s School of Earth Sciences and lead author on the study, said: “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.”
