Joe Smith, an ornithologist, explains that birds have the amazing ability to see a whole spectrum of colors that are invisible to us, people. Back in 2007, scientists, with the help of a spectrophotometer, analyzed the colors of 166 North American songbird species which did not have an apparent physical difference between the sexes. From a human’s perspective, in 92 percent of species, both males and females look identical. However, the study showed that these birds have colors that are simply undetectable by our eye that they differentiate their genders by.