There are Bluebirds …
and then there are really blue birds.
Blue Grosbeaks are a rarity in this part of Minnesota, but they are another example of a species that is expanding its range northward in recent decades as forest land is cleared for housing development and agriculture. They favor patches of shrubs and deciduous trees and old farm fields to set up housekeeping and raise a family before flying back to their winter headquarters in Mexico and Central America.
Indigo Buntings and their relatives the Blue Grosbeaks are some of the bluest of blue-colored birds. Blue Jays and Bluebirds pale (literally) in comparison to the deep blue color of the two buntings (grosbeaks are technically a type of bunting).
As you may know, birds do not have blue pigments in their blue feathers — the color is achieved by structural elements in the feather (keratin deposits that surround small air pockets) that reflect the short wavelength blue color back to the viewer’s eye. Without this structural interference in the transmission of light through the feather, it would look brown — the color of the underlying melanin pigment.
So, why are some birds so much bluer than others, males bluer than females, Indigo Buntings and Blue Grosbeaks bluer than Blue Jays? Inquiring minds want to know…but there don’t seem to be answers, other than vague references to the importance of bright colors in males compared to females. And here’s another thought to ponder: are “blue birds” blue to other birds — or can they see patterns in the blue reflected light because they can see/process shorter wavelength light than humans can?