WING-STRIPE METRICS FOR IDENTIFYING SUBSPECIES OF THE ROCK SANDPIPER

Abstract

Identification in formative and basic plumage of two of the three subspecies of the Rock Sandpiper breeding in Alaska—Calidris ptilocnemis tschuktschorum and C. p. couesi—remains problematic, although a difference in the white wing stripe has been reported qualitatively. For all three of Alaska’s breeding subspecies, including C. p. ptilocnemis, I used three criteria to quantify the wing stripe on each of the inner primaries and on the outer and middle secondaries of numerous specimens and birds photographed. The white stripe is significantly more extensive in tschuktschorum than in couesi, and even more extensive in ptilocnemis, but there is overlap, especially near the zones of contact between the subspecies. The combined criteria can support subspecific identification, of at least some Rock Sandpipers, even in the formative and basic plumages.