California Hummingbirds Rapid Evolutionary Change

With plenty of artificial nectar available, Anna’s hummingbirds have expanded their range northward and their beaks have become longer and larger.

An Anna's hummingbird

"Though we often think of evolution as happening slowly, over hundreds of thousands or even millions of years, it can - and often does - occur “literally in front of our eyes"... And we just need to pay attention to it," says Alejandro Rico-Guevara, an evolutionary biologist at the University of Washington, and co-author of a new study that reveals the remarkable and rapid evolutionary change in these hummingbirds.

According to the study, the beaks of Anna’s hummingbirds (Calypte anna) have grown longer and larger over just a few generations, thanks largely to the proliferation of hummingbird feeders after World War II. In addition, the growing popularity of hummingbird feeders has allowed the tiny birds to expand their range northward, from Southern California all the way up the coast to British Columbia.

To understand how Anna’s hummingbirds have changed, scientists gathered and analyzed data from a variety of sources, from as far back as 1860, and discovered how human activities have unwittingly shaped the Anna’s hummingbird over time. First, the widespread planting of eucalyptus trees starting in the mid-1800s seems to have allowed the petite birds to begin expanding their range, but once hummingbird feeders became popular amongst households, the birds really began to thrive. Their range continued to grow, and their bodies adapted to the artificial abundance of food.

Researchers saw changes over the course of just about ten generations.

Anna’s hummingbirds are far from the first species to adapt to human-caused changes to their environment. In fact, Alexandre was initially inspired to conduct the study after learning about how seed feeders in the UK may have caused the beaks of great tits to grow longer than their counterparts in the Netherlands.

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