Cliff Swallows Evolved Quickly Due to Climate Change


Typically, you expect population genetics to take millions of years. And while cliff swallows didn't turn into different species, they have evolved through natural selection in a surprisingly short time – just 30 years. A 30-year study of cliff swallows, a long-distance migrant bird species, has revealed that global climate change is altering their breeding habits.


According to the Audobon Society "Every year an estimated 80 million birds, of all species, are killed by vehicles in the United States, and those numbers are likely rising, say experts. However, a new report in Current Biology shows one population of cliff swallows in Nebraska is bucking that trend, possibly by adapting to an increasingly urban environment at a breakneck pace. During a span of 30 years scientists recorded body measurements of cliff swallows that were killed by cars along the same route in southwestern Nebraska, and compared them with swallows from the same population that had been caught in mist nests. The researchers found the mist-netted birds had significantly shorter and sleeker wings, suggesting those animals might be advantageously adapted for pivoting and dodging oncoming traffic.


At the same time, the number of road-killed birds plummeted—from 20 birds a year at the start of the study in 1983 to two last year—while the number of cliff swallow nests mushroomed from 5,000 to 25,000. The researchers say there could be multiple adaptive strategies at work. They note that cliff swallows are tremendous observers, so they may have learned to avoid vehicles over time by watching what happened when birds didn’t dart away from cars and buses. Perhaps natural selection is favoring intellectual birds, which then pass their knowledge onto their offspring. And while cliff swallows didn't turn into different species, they have evolved through natural selection in a surprisingly short time – just 30 years. “In evolutionary terms, 30 years is an instant in time,”