Cassin's Sparrow

Peucaea cassinii

Order:
Passeriformes
Family:
Passerellidae
Sections

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Alternate Cassin's Sparrow.

Long-tailed sparrow with indistinct buffy-gray supercilium and pale lemon bend of wing. Tips of outer rectrices are whitish. Bill is long, with relatively straight culmen. When fresh, Formative, Definitive Basic, and Alternate Plumages are similar. But by late summer, Alternate Plumages are noticeably plainer and duller due to feather wear: the upperparts lose their variegated appearance and are almost unstreaked.

Alternate Rufous-morph Cassin's Sparrow.

Rufous morph is brighter overall with more rufous upperparts, wing and tail edgings, and uppertail coverts. The indistinct streaking to the breast sides is a juvenile character that could indicate a first-year. But in this case it more likely represents variation in Alternate Plumage, perhaps due to molt timing that could occur in either first-year or older birds.

Formative or Definitive Basic Plumage Cassin's Sparrow.

Nape and sides of neck are gray with rufous-brown (some blackish-brown) streaking. Upperwing coverts with grayish to rufous-brown centers, the smaller lesser coverts fringed pale buff to yellowish and the median and greater coverts with buff-gray outer edges, forming indistinct wing-bars. Formative and Definitive Basic Plumages are largely indistinguishable following complete Preformative or Definitive Prebasic Molts, respectively.

Formative or Definitive Basic Plumage Cassin's Sparrow.

Underparts are pale brown or gray to whitish, the chin with indistinct dark-gray malar stripes, the upper breast darker and washed buff, the sides and flanks paler. Belly is dull white.

Formative or Definitive Basic Plumage Cassin's Sparrow.

Formative and basic back feathers and scapulars are pale brown with broad gray edges, dark-brown subterminal spots or irregular bars, and often thin brown shaft streaks or spots, resulting in a variegated pattern of pale gray and warm brown with dark crossbars or spots rather than streaks.

Cassin's Sparrow.

Forehead and crown are gray and finely streaked with dark brown. Superciliary stripe is grayish, becoming more pale and buffy above lores (washed pale yellow when fresh); postocular stripe is light cinnamon-brown. Moderately distinct dull white eye-ring is present. Flanks and sides are pale gray and may be striped with a few brown or dusky streaks, especially posteriorly. By this date most birds have commenced the Prealternate Molt and are thus in a transitional plumage.

Cassin's Sparrow tail.

Uppertail coverts are gray-brown with narrow pale gray edges and prominent dark brown subterminal crescent. The central rectrices are brownish gray with a darker serrated shaft streak and imperfectly developed crossbars. The remaining outer rectrices are dusky gray-brown, the outer three with noticeable pale gray to whitish tips (becoming whiter distally) and margins to outer webs, with largest and palest tips to r6. This bird could either be in Formative or Definitive Basic Plumage, which are not separable after the fall molts.

Auxiliary Formative Cassin's Sparrow.

This is the first of two post-juvenile plumages and results from a partial Auxiliary Preformative Molt, which occurs prior to the complete Preformative Molt. First-fall migrants are often in this plumage. Note that the visible median coverts and some inner greater coverts have been replaced, and contrast in freshness with the remainder of the wing feathers, which are retained juvenile. It also appears that central back feathers may be replaced, contrasting with juvenile scapulars. The underparts are variably streaked in this plumage, usually less so than in Juvenile Plumage.

Juvenile Cassin's Sparrow.

The throat with short streaks or spots and the breast, sides, and flanks considerably streaked dark brown to brown-gray. Sides of head dull buff, streaked with buffy brown; auriculars and lores margined buff. Underparts are buffy, with paler whitish belly.

Example of Cassin's Sparrow habitat in Arizona.

Arid grasslands with scattered shrubs, yuccas, or low trees such as mesquites and oak. Near thickly vegetated draws, prefers open slopes, rarely going into dense brush.

Cassin's Sparrow on Opuntia cactus.

Habitat in breeding range also includes ground layers dominated by grasses, or forbs and cactus (Opuntia spp.) in overgrazed areas.

Example of Cassin's Sparrow habitat in Texas.
Cassin's Sparrow with prey item.

Main foods taken include insects during the nesting season, and weed and grass seeds during the nonbreeding season.

Cassin's Sparrow vocalizing.
Cassin's Sparrow skylarking.

When giving Flight Song (“skylarking”), male flies directly upward, giving introductory notes as the male rises with trembling wing strokes at an angle of 30°–60°. Male then floats downward on set wings while singing trill, final two descending notes given just before landing.

Cassin's Sparrow skylarking.

Flight posture has head up, tail fanned, legs stretched downward.

Cassin's Sparrow skylarking.
Cassin's Sparrow nest, Arizona.

Nest is on ground or in low shrub or grass clump, usually within 20 cm of ground. Specimen collected 12 mi N Sonoita, Pima County, Arizona. 1 August 1970. Ruler is 8 cm.; photographer Rene Corado.

Cassin's Sparrow clutch, Arizona.

Eggs are white, unspotted, and slightly glossy. Collected 12 mi N Sonoita, Pima Co., AZ. 1 Aug.; photographer Rene Corado.

Cassin's Sparrow nest, Arizona.

Full clutch of eggs. Santa Cruz Co., AZ; June.; photographer Rick and Nora Bowers.

Cassin's Sparrow chicks in nest.

Chicks are altricial and naked except for sparse, light-gray down on head and back, and pronounced yellow rictal flanges. Mouth lining is dark red with two parallel yellow lines on upper palate and two yellow spots on floor of mouth as feeding targets.

Cassin's Sparrow (cover image).

Recommended Citation

Dunning, J. B., Jr., R. K. Bowers Jr., S. J. Suter, and C. E. Bock (2018). Cassin's Sparrow (Peucaea cassinii), version 2.0. In The Birds of North America (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.casspa.02