Palm Warbler - Setophaga palmarum

Palm Warbler has a partial preformative molt and limited prealternate molts that are restricted to head feathers. Plumage differs subtly by age and sex, such that age is most reliably determined prior to completion of skull ossification in fall, and sex is often identifiable only through brood patch or cloacal protuberance during the breeding season, although some males can be recognized by plumage.

The two subspecies of Palm Warbler (Western Palm Warbler, S.p. palmarum, and Yellow Palm Warbler, S.p. hypochrysea) are generally separable by plumage, but guidelines for age and sex determination are applicable to both.

Quick tips

• Check the primary coverts - on FCF/FCA (HY/SY) birds they may appear slightly pointed and a bit paler brown than the replaced greater coverts, whereas on DCB/DCA (AHY/ASY) birds they tend to be somewhat more rounded and the wing is uniformly brown.
• Look at the tail - on FCF/FCA (HY/SY) birds the outer rectrices tend to be slightly paler and narrower, and with somewhat smaller white spots than on DCB/DCA (AHY/ASY) birds, but the differences can be subtle and only extremes are helpful for ageing.
• Examine the crown - in fall and winter, any individual with a rusty patch greater than 5 mm long is likely to be a DCB (AHY) male, but DCB (AHY) females and FCF (HY) males can also have smaller rusty patches; in alternate plumage, the longest rusty crown patches (19-21 mm) are indicative of DCA (ASY) males, but the length largely overlaps for other age/sex classes.

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