American Tree Sparrow - Spizelloides arborea

American Tree Sparrow has a partial preformative molt, and limited prealternate molts that are largely restricted to body feathers but can occasionally include tertials and central rectrices. Although molt limits and rectrix shape can be helpful, both are often subtle, and especially by spring a fair number of intermediates cannot be reliably aged and are best considered M-FCF (AHY). Sex of most individuals is reliably determined only via brood patch / cloacal protuberance during the breeding season.

Quick tips

• Look at the tail - uniformly narrow and pointed rectrices OR contrastingly fresh and broad central rectrices are indicative of FCF/FCU (HY/SY), while uniformly broad and more rounded rectrices are typical of DCB/DCU (AHY/ASY).
• Check the wing for molt limits - a slight contrast between darker/fresher greater coverts and tertials vs. the paler block of primary coverts, primaries, and secondaries is typical for FCF/FCU (HY/SY), while a wing more uniform in colour and wear suggests DCB/DCU (AHY/ASY).

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