Many birds are adapting to the changes taking place in the world around them.  An excellent example of this is the eyes of some birds living in brightly lit habitats are actually getting smaller.  Jennifer Phillips, assistant professor in Washington State University’s school of the environment explains the situation this way, “Animals living in a bright area don’t need to gather so much sunlight.”

       For some time, biologists have known that the eyes of birds that live their lives in dark forests are larger than those inhabiting locales bathed in natural sunlight. A similar phenomenon seems to exist with birds living in well-lit cities. Here some birds have smaller eyes than those that make their home outside of the inner city. This is thought to be due to city birds have to live in the constant glare of bright city lights.

      In an effort to test this theory, Phillips and her research team used mist nests to capture Carolina wrens and northern cardinals in and around San Antonio, Texas.  The researchers carefully measured the size of the eyes of all birds netted. They recently published the results of their study in Global Change Biology.  Their findings demonstrated the Carolina wrens and northern cardinal living in the brightly lit core of San Antonio were smaller than their counterparts inhabiting the perimeter of this large Texas city. Phillips interpreted the findings this way, “That makes sense. If you’re trying to build a nest or sleep in bright urban areas, it’s likely beneficial to have smaller eyes.”