Ruby-crowned Kinglet - Regulus calendula

Ruby-crowned Kinglet has a partial preformative molt, and absent to limited prealternate molts that are difficult to detect. This species can be relatively difficult to age, as age-related differences in wing and tail patterns are often subtle; especially by spring, when a fair number of intermediates cannot be reliably aged and are best considered M-FCF (AHY), unless wing and tail cues clearly agree on a particular age. Individuals showing their ruby crown are easily recognized as males, but this feature is often concealed and females should be identified with greater caution.

Quick tips

• Examine the crown - females lack red feathers, while males have a central red patch, but note that it may be well concealed.
• Check the shape of the outer rectrices - on FCF/FCU (HY/SY) birds they are narrow and pointed, while on DCB/DCU (AHY/ASY) birds they tend to be more broad and rounded; however, there are many intermediates that are difficult to classify.
• Look at the primary coverts - on many FCF/FCU (HY/SY) birds they are narrow and pointed (with minimal green edging remaining by spring), while on DCB/DCU (AHY/ASY) birds they tend to be more broad and rounded (with distinct green edging retained through spring).
• Examine the inner greater coverts - on a small minority of FCF/FCU (HY/SY) birds up to three feathers are replaced and are slightly longer and darker than the adjacent older feathers, but uniform greater coverts can be seen at all ages.

Species account prepared by McGill Bird Observatory (2018). Last updated by Marcel Gahbauer (Mar 2022)