Fox Sparrow - Passerella iliaca

Fox Sparrow has a partial preformative molt and absent to limited prealternate molts. Age-related differences in wing and tail patterns are often subtle; especially by spring, a fair number of intermediates cannot be reliably aged and should be considered M-FCU (AHY). Sex can generally be determined only by brood patch / cloacal protuberance during the breeding season, or by particularly short or long wing chords (e.g., for the eastern race <83 mm = female, >89 mm = male).

The four recognized subspecies differ somewhat in appearance and extent of molt, but the overall patterns are sufficiently consistent for ageing/sexing guidelines to apply to all of them.

Quick tips

• Look at the tail - outer rectrices are typically narrow and pointed on FCF/FCU (HY/SY) individuals, while broad and more rounded outer rectrices are typical of DCB/DCU (AHY/ASY).
• Check the outer primary coverts - they are relatively narrow and pointed with minimal pale brown edging on FCF/FCU (HY/SY) birds, compared to relatively broad and rounded with distinct rufous edging on DCB/DCU (AHY/ASY) birds.

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