Keeping an eye on those pesky Tree Swallows

Mountain Bluebirds are back, and I was so happy to see this colourful male, perched near a nesting box, SW of the city, on 8 May 2014. There were several Tree Swallows circling over and around a nearby nest box and the Bluebird was keeping an eye on them. I thought this might be the same male that used this nest box last year, but I noticed that this one has not been banded.

In Bluebirds, the blue colour is produced by the structure of the feather - there is no blue pigment. "Tiny air pockets in the barbs of feathers can scatter incoming light, resulting in a specific, non-iridescent color. Blue colors in feathers are almost always produced in this manner. Examples include the blue feathers of Bluebirds, Indigo Buntings, Blue Jay's and Steller's Jays."

www.allaboutbirds.org/guide/Mountain_Bluebird/id

www.jstor.org/discover/pgs/index?id=10.2307/4077277&i...