Song Sparrow has a partial to incomplete (rarely complete) preformative molt, but lacks prealternate molts. Because the preformative molt can be complete and many intermediates are difficult to age in spring, caution should be exercised with ageing unless retained juvenile feathers are visible. Sex can be determined only by brood patch / cloacal protuberance during the breeding season.
Juvenile plumage is very similar to that of Lincoln's and Swamp Sparrows; Song Sparrow tends to have a proportionately longer tail, and distinctly wide malar stripe.
Species account prepared by McGill Bird Observatory (2016). Last updated by Marcel Gahbauer (Mar 2022)
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FCJ - (HY: April - September) | ||
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Somewhat dull and grayish, with indistinct streaking on the underparts | ||
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M-FCF - (U: December - December; AHY January - October) | ||
Rectrices all relatively broad and rounded; outer primary coverts relatively broad and rounded, with reddish-brown edging; primaries and secondaries uniformly dark; iris distinctly brown | ||
U |
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FCF - (HY/SY: July - following October) | ||
Rectrices all relatively narrow and pointed or mixed with fresher, broader, and more rounded feathers; outer primary coverts relatively narrow and pointed with minimal gray edging; primaries and secondaries uniformly paler than coverts or showing blocks of darker replaced feathers after an eccentric molt; iris grayish-brown until early-mid winter | ||
U |
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FPJ - (HY: April - August) | ||
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Similar to FCJ; some natal down remaining and/or juvenile flight feathers still growing in | ||
U |
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FPF - (HY: July - November) | ||
Similar to FCF; median and greater coverts and tertials being replaced; occasionally also some to all rectrices and primaries being replaced; iris grayish | ||
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M-SPB - (AHY: July - October) | ||
Flight feathers being replaced, with retained feathers not distinctly pale or worn; iris brown | ||
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SPB - (SY: July - October) | ||
Flight feathers being replaced, with retained juvenile primaries, secondaries, and/or primary coverts distinctly pale brown and very worn; iris brown | ||
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