Swallows are evolving to avoid being run over on highways.

In Nebraska, United States, terns have developed the ability to more easily escape the continuous and fast-moving highway vehicles. A study by Charles and Mary Brown of Tulsa University says that Southern Swallows have smaller wings, which allows them to escape from cars or trucks at higher speeds.

As the region's swallows are used to nesting in risky places such as bridges and overpasses, the only surviving chicks are those that can escape the danger of cars. The swallows that are found dead have wider wings than those that live with cars, proving the researchers' conclusion.

Studies with swallows 30 years ago reveal a greater number of animals killed at the time, and birds with larger wings as well. Another hypothesis is that swallows have simply learned to avoid cars, but there is no plausible explanation for wing size reduction.

This case is a clear example of how human intervention can change the behavior and development of certain animals, especially when we directly interfere with the ecosystem in which they operate.