North American Birds

VOLUME 70 NO3-NO4 2019

A Quarterly Journal of Ornithological Record Published by the American Birding Association. The mission of the journal is to provide a complete overview of the changing panorama of our continent’s birdlife.

Issue link:

Contents of this Issue


Page 12 of 163

259 V O L U M E 7 0 ( 2 0 1 9 ) • N U M B E R S 3 / 4 RED-BACKED SHRIKE IN ALASKA the distinct pale outer edge shown by Red- backed and the Gambell shrike. • ISABELLINE SHRIKE: In Isabelline Shrike of the nominate subspecies, wing and tail morphology is similar to that of Turkestan Shrike, averaging shorter than that of Red- backed and the Gambell shrike. In juveniles and first-fall birds, the upperparts are a paler, 2015). The outer rectrix is also intermedi- ate in relative length between that of Brown and Red-backed shrikes, with a ratio of r5- r6/r6 to the tail base being 0.113–0.181 mm. These ratios on the Gambell bird (see above), though better for Red-backed Shrike, could also apply to Turkestan Shrike. As shown in fig 11, the outer rec- trix of Turkestan Shrike also does not show The tail is also more graduated in Brown Shrike (fig 8) than in Red-backed Shrike. They have an obviously shorter outer rec- trix (r6), which is also thinner than other rectrices, whereas in Red-backed Shrike and the Gambell bird the outermost rectrix is broader (Svensson 1992; fig 5 and 7D) and its tip falls closer to those of the lon- gest tail feathers (fig 3, 5, 6, and 7D). The ratio of r5–r6/r6 to the tail base shows a range of 0.248–0.364 in Brown Shrike and 0.091–0.157 in Red-backed Shrike (Pyle et al. 2015). In the Gambell bird, these ra- tios showed a range of 0.096–0.161 (mean 0.140) in six images (e.g., fig 7C–D), again matching Red-backed Shrike and outside the range of Brown Shrike. As shown in fig 8, many Brown Shrikes do not show as clear a pale edge to the outer rectrix, as that edge is thinner and tinged with buff or pale-brown rather than the broader, whiter edge of Red- backed Shrike and the Gambell bird (fig 3, 5, 6, and 7B). However, such differences in outer rectrix coloration may be only slight in some individuals. • TURKESTAN SHRIKE: Juvenile Tur- kestan (fig 11A–-B) and Isabelline shrikes show a much duller, gray-brown to grayish head and mantle compared to Red-backed Shrikes (fig 11C–D) and the Gambell bird, lacking the latter's warm tones. The mantle is plainer, lacking vermiculations or having fainter (narrower and finer) and more re - stricted barring. There is typically a distinct contrast between the grayer upperparts and warmer-colored tail in Turkestan Shrike, whereas Red-backed Shrike and the Gambell bird show no such obvious contrast (fig 3, 6, and 11A–D). Juvenile Turkestan Shrikes do not show a contrasting grayish nape, and the mask typically lacks the rufous tones shown by many juvenile Red-backed Shrikes and the Gambell bird. The flanks in juvenile Turkestan Shrike are whitish or cream, rather than pale buff as in some Red-backed Shrikes and the Gambell bird. In Turkestan Shrike, the preformative molt on summer grounds often includes most body feathers, upper - wing coverts, and tertials, befitting a shorter- distance migrant, being more extensive than shown by the Gambell bird, although caution is warranted in applying molt locations and extents to identification (Pyle et al. 2015). Turkestan Shrike has a long primary pro- jection, although not quite as long as Red- backed, with the tip of p9 falling between p5 and p6 and a ratio of p8-p9/p9-primary coverts being 0.136–0.230 (Pyle et al. Figures 10A–B. These two photos show more typical field views of the Gambell Red-backed Shrike on 7 Oct 2017 (A) and of a first-fall Brown Shrike at Gambell on 29 Aug 2014 (B). Compared to the Red-backed Shrike, the Brown Shrike lacks a gray nape, has a thicker bill, weaker vermiculations above, a blacker face-mask, and shows slightly shorter primary projection. This photo of the Gambell Red-backed Shrike was the first distributed off- island by Lehman and is the image which first alerted Hough that a Red- backed Shrike rather than a Brown Shrike might be involved. Photos by © Clarence Irrigoo Jr. (A) and © Paul E. Lehman (B) A B

Articles in this issue

Archives of this issue

view archives of North American Birds - VOLUME 70 NO3-NO4 2019