These bluebirds are residents here all year. The first was abandoned but we now have eggs and chicks in two nest boxes. After cool weather, it is now warmer and insects have hatched for parent birds to stuff in the wide beaks of demanding youngsters. They often fly to the ground from a perch for a morsel invisible to us. From a distance, the male plumage looks slate-blue but close-up in the sun they are gorgeous blue and rouge. Evidently, the blue color is created by light scattering (like a prism) whereas pigment is responsible for their sky blue eggshells. Why they are blue to match plumage when many other cavity nesters have white eggs with or without speckles is a question I can’t answer. Recent research confirms that birds tend to be more colorful in the tropics, but our bluebirds are among many exceptions to the rule.
By Roger Gosden
British-born scientist specializing in reproduction & embryology. Career as professor & research director spanned from Cambridge to Cornell's Weill Medical College in NYC. Married to Lucinda Veeck Gosden, embryologist for the first successful IVF team in America. Retired early to Williamsburg, Virginia, to write and recover from 'nature deficit disorder'. Currently a visiting scholar at William & Mary. https://en.wikipedia.org/wiki/Roger_GosdenView all of Roger Gosden's posts.