Eastern Bluebird - Sialia sialis

Eastern Bluebird has a partial to incomplete preformative molt but no prealternate molt. Sex can be easily determined by plumage, with males always showing more blue than females of the same age class. Age is also often readily apparent from overall appearance, but in case of doubt, closer examination of the wing and/or tail generally allows for quick confirmation.

Quick tips

• Look at the greater coverts - the presence of a molt limit between fresh blue inner and older brownish outer feathers or between uniformly fresh greater coverts and contrastingly older and browner primary coverts indicates a FCF (HY/SY) bird, whereas DCB (AHY/ASY) individuals have more uniformly fresh greater and primary coverts.
• Examine the rectrices - if all are relatively narrow or there is a mix of narrow and fresher, broader rectrices this indicates an FCF (HY/SY) individual, but note that uniformly fresh and broad rectrices can occur on both DCB (AHY/ASY) individuals and FCF (HY/SY) birds with a particularly extensive preformative molt.
• Consider the upperparts - only DCB (AHY/ASY) males are solid bright blue above; FCF (HY/SY) males are mostly blue with a grayish tinge, DCB (AHY/ASY) females are mostly grayish with a bluish tinge, and FCF (HY/SY) females are largely grayish with limited blue.
• Consider the underparts - FCJ (juvenile) birds are heavily spotted, similar to other thrushes.

Species account prepared by McGill Bird Observatory (2016). Last updated by Marcel Gahbauer (Mar 2022)