Evolution happens. Even in Oklahoma.
In Tulsa, Oklahoma, over the last 30 years, the number of cliff swallows killed by moving vehicles has drastically decreased. That change can't be accounted for by alterations in traffic patterns or swallow populations, say scientists. Instead, they think it's tied to the fact that the birds' wingspan is also decreasing
. This adaptation — whether selected for by vehicular birdicide and/or other factors — helps swallows be more nimble in the air at high speeds, making it easier for them to avoid oncoming traffic. (EDIT: Sorry guys, I made an error here. Some of the researchers were from Tulsa, but study actually happened in Nebraska. Evolution takes place throughout the plains states.)