ML646594750

Observation details

**very rare; first Suffolk and second NYS record. Found yesterday by Max Epstein; refound this morning by Bon Pron. Medium-sized Passerellid sparrow, superficially unremarkable-looking, being grayish and subtly patterned. It appeared large-headed and squat, with a flattened feeding posture; these, together with its mostly grayish appearance recalled Ipswich Sparrow. But the maxilla was deeper than the mandible and gently down-curved, following the chord of the crown--very unlike the more handsome genera, Passerculus, Melospiza, Spizella, etc. Together, the flat crown, asymmetric bill shape, and complexly marked, white-black-maroon-gray feathers of the upperparts recalled Grasshopper Sparrow (an errant individual of which was also present, near to and sometimes associating with the present bird, behaving in almost exactly the same way). The crown was very neatly and finely streaked with white, brown, and black, like the mantle feathers in miniature, contrasting subtly with the paler (but still vaguely streaked) supercilium and the more richly brown (but also subtly streaked) auricular. A neat white eyering was present but not very conspicuous against the similarly pale supercilium. The underparts were mostly pale and unmarked but nevertheless flecked with small, short, indistinct streaks, most conspicuous along the most dorsal level of the flanks, especially toward the rear, and very small and inconspicuous on the breast and along the more ventral parts of the flanks. The median and greater secondary coverts showed white edges that framed the black-maroon centers of the greater coverts with moderately neat white wingbars; the tertials were broadly dark-centered with distinct whitish edges all around (see description of wear and molt, below). These features, together with its posture and habits, recalled Lapland Longspur. But unlike all of those comparison species, this bird had a long (albeit worn and incomplete) tail--as long as a Song Sparrow's, or possibly longer. These feathers appeared mostly dark, with white tips to the outer feathers (the latter point good for Cassin's Sparrow), but lacking the delicately cross-barred, Sturnella-like pattern to rr1 that is an important field mark of Cassin's Sparrow (learned from Tom Burke in the context of NY's first record, discovered by him and Gail Benson in October 2000). Our suspicion here, which was confirmed through critical photos from Mike Cooper and Tim Healy) was that the central tail feathers (rr1) were missing. Viewed from the rear, the tertial panels were strikingly asymmetric: those on the left wing presented as large, with black centers and broad, very neat white margins all around; but the innermost tertial on the right wing was noticeably smaller, brown-centered, and with a heavily worn, very narrow pale margin, as expected in a retained juvenal feather. We noticed in the field that the next tertial on the right wing appeared larger, blacker, and less worn than the feather above it, which is an odd combination, because replacement of the tertials typically goes from proximal to distal. Perhaps the bird simply skipped the innermost tertial on the right wing? But the situation is more complicated than that, because photos seem to show that t2 is growing in on the left wing, even though t3 appears already to have been fully replaced. I have not seen spreadwing shots yet (8 Dec 25), but the primaries appeared very brown and worn. The absence of rr1 is not unexpected, as these are normally the first rectrices to be replaced in an actively molting bird. In the East, the combination of fresh coverts and tertials in contrast to worn and brown flight feathers in a nine-primaried oscine in December generally indicates a hatching-year individual. But some southwestern North American species have more complicated molt strategies, with supplemental molts in addition to the standard pre-basic molt, as well as long-distance movements between breeding areas, molting/staging areas, and wintering areas, with replacement of various feather groups suspended or delayed across these times and places. Per Pyle, adult CASP undertake a complete pre-basic molt on the breeding grounds prior to migration, whereas juvs have a more complicated strategy, replacing body plumage on the breeding grounds during Jun-Sep, then replacing body plumage again, and also the flight feathers, "on the summer and/or winter grounds" during Sep-Nov. Thus the Montauk bird's state of active molt, at a site far from the breeding areas, is at odds with an adult, but consistent with a hatching-year bird (albeit somewhat delayed and slightly eccentric regarding the sequence and asymmetry of tertial replacement). As suggested below, it is possible that this bird, as well as other vagrants from the Southwest (which the Montauk GRSP might even be an example of), are responding to the severe drought there this year. As described above, the details of the bird's structure and feather patterning are spot-on for the genus Pucaea, and the finely streaked crown, small bill (relative to Botteri's), overall grayish aspect, and the detailed patterns of the mantle, uppertail, wing coverts, tertials, and outer rectrices, all indicate Cassin's Sparrow rather than Botteri's or Bachman's. To be thorough, we considered non-Passerellid taxa as well, ruling out Palearctic emberizid buntings by bill shape and tertial pattern (among other things), and various weavers, bishops, and others (less certainly) by the short tails of female bishops and some of the others--but mainly via the detailed resemblance of multiple different feather patterns to those of Cassin's Sparrow. Like many typically skulky species (cf. GRSP), CASP is undoubtedly under-detected as a migrant/vagrant, but those birds that we do find are often amazingly confiding (recent examples familiar to LI birders include Corn Crake, Purple Gallinule, Smith’s Longspur, and many others—as well as countless Soras, Virginia Rails, and American Woodcocks on city streets). Hindsight might show that this record aligns with others (Broad-billed Hummingbird and Cave Swallow come to mind) consistent with a broader pattern of vagrancy from the Southwest this season, possibly related to the extreme drought there this year.