Canada Warbler - Cardellina canadensis

Canada Warbler has a partial preformative molt, and limited to partial prealternate molts that are restricted primarily to body feathers but can include up to three inner greater coverts in the first cycle. Sexes can overlap in appearance during the first cycle; especially by spring age determination can be challenging as differences in key characteristics are often subtle, and therefore some intermediates are best considered as M-FCU (AHY).

Quick tips

• Look for molt limits on the wing - on DCB/DCU (AHY/ASY) birds the wing is uniformly gray, while on FCF/FCU (HY/SY) birds there is often a visible contrast between the gray greater coverts and brownish-gray primary coverts, primaries, and secondaries.
• Examine the forehead - it is moderately to extensively black on all DCB/DCU (AHY/ASY) males and FCU (SY) males, and has black flecks on some DCU (ASY) females and FCF (HY) males, but is greenish-gray and lacking black on other DCU (ASY) females and FCF (HY) males and all FCF/FCU (HY/SY) females.
• Consider the rectrices - on FCF/FCU (HY/SY) birds they are relatively narrow and pointed, while on DCB/DCU (AHY/ASY) birds they tend to be broader and more rounded, but there is considerable variation, and only extremes may be useful in helping with ageing.

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