Researchers from Uppsala University and the Swedish University of Agricultural Sciences reported the first phylogenetic analysis of the evolution of violet sensitive and ultraviolet sensitive vision in modern birds in a Feb. 10, 2013, article in the open access journal BMC Evolutionary Biology.
All modern daytime birds either have violet sensitive or ultraviolet sensitive vision that involves the genes responsible for producing the light sensitive pigment (SWS1 opsin).
The sequencing of the SWS1 opsin from 40 species of birds, in 29 families, indicated that the pigment changed at least 14 times over the long history of modern day birds. Ultraviolet sensitive vision alters visual cues used to select a mate, avoiding predators, and in finding food.
Modern day birds have existed for 95 million years. The changes in the pigment that produces ultraviolet sensitive vision could have been the result of climate changes that altered the most prominent frequencies of light available to birds and other animals.
The variations in the available frequencies of light produced by volcanic debris in the atmosphere that lasted for long periods of time, slight alterations in the Earth’s orientation to the Sun, and other factors could have promoted the alterations seen in bird’s sight.
Once the gene changed, the trait was passed on to subsequent generations and species that evolved from a common ancestor. This sequence of events allowed the researchers to back track bird’s ultraviolet sight evolution.