The large blue birds that fly around the vast 1,200 square mile wilderness area of Yosemite National Park go by many names including long-crested jay, mountain jay, and pine jay but they are officially called Steller’s Jay (Cyanocitta stelleri).
Yosemite’s unusually diverse habitats are home to 165 resident and migratory species and there have been an incredible 262 species of birds documented inside the park. Visitors may be treated to rare bird sightings like the white-face ibis that showed up in April 2011 but they can reliably expect to see scores of Steller’s Jays which are one of the most common birds in the park.
While outwardly appearing to be blue, Steller’s Jays coloration is actually an optical illusion as pointed out in a recent social media post by Yosemite National Park:
When is a bluebird not blue? The answer: always!
The Steller’s jay is one of the most common birds visitors see in Yosemite National Park. They are known for their plumage of bright blue and black feathers and distinctive triangular-shaped crests. The Steller’s jay is a type of corvid often referred to as a blue jay. But here’s the kicker…there’s actually no such thing as a “blue” jay. It sounds unbelievable, right? Those birds look blue! But, in reality, the blue coloration is an illusion of light.
Birds with yellow or red feathers usually get their color from pigments in their food. For example, the pink that gives flamingos their signature color results from eating shrimp. But blue pigments, like those in blueberries, are destroyed when digested. This means that no bird species can make blue from a pigment.
So why do we see blue feathers? Blue is a ‘structural color’ created by proteins called keratin (the same stuff your fingernails are made of). As the feather grows, the keratin builds to create a pattern. Visible light strikes these patterns in a way where all other colors pass through the feather except blue. Blue is instead reflected to our eyes, so we see blue!
If you grind up the red-pigmented feathers of a cardinal, the powder will be red. But, if you do the same with a Steller’s jay feather, the powder will be brown. Once the patterns of protein in the feather are destroyed, the Steller’s jay’s true colors are revealed.
Incredible to realize that Steller’s Jays’ blue appearance is due to the microscopic structure of their feathers scattering light and reflecting blue wavelengths rather than actually containing any blue pigment.
As a reminder, Steller’s Jays are inquisitive birds that like to forage on insects, seeds, nuts, eggs, and small animals but will happily eat human food if left unattended or not properly disposed of. Keep a clean campsite and make sure not to litter when visiting any and all National Parks.
