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: http://nab.aba.org/i/1115839

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RED-BACKED SHRIKE IN ALASKA 256 N O R T H A M E R I C A N B I R D S the pale yellowish to pinkish bill base of the Gambell shrike clearly indicated that it was a first-fall bird. Careful scrutiny of the images indicated that the bird was still largely in ju- venile plumage but with scattered newer for- mative feathers present in the crown, scapu- lar tract, and among the lesser coverts (fig 1, 3, 4, and 6). These formative feathers were reddish-brown and either lacked or showed very indistinct barring, contrasting with the more worn and heavily barred juvenile feath- ers. Some newer white formative feathers, without barring, may also have been pres- ent in the supercilium, malar region, throat, and breast, while some new blackish feath- ers may have been present in the lores and auriculars. The preformative molt in these shrikes can begin on the summer grounds, suspend for migration, and continue at stop- over locations (Pyle et al. 2015), and it ap- pears that this bird had replaced some juve- nile feathers before reaching Gambell. Sexing of birds in this plumage is not recommended. The darker juvenile remi- ges may indicate a male (L. Svensson in in correct identifications. Molt strate- gies and age determination in this group have been discussed by Svensson (1992), Cramp and Perrins (1993), and Panov et al. (2011), and they were summarized by Pyle et al. (2015). The extensive barring to the upperparts and underparts and Figure 5. The Gambell Red-backed Shrike in flight, 10 Oct 2017. Note the wing and tail morphology including un-emarginated p6 and relatively long and broad outer rectrix, as compared with that of Brown Shrike. See Figure 7C, right, for details. Photo by © Sue Bryer Figure 6. The photo below of the Gambell Red-backed Shrike, taken 19 Oct 2017, shows many of the important characters used in its identification: thinner bill than Brown Shrike and with more exten- sive pale coloration to the base, extensive dark vermiculations to the mantle, sides, and flanks, a low-contrast face-mask, a contrasty grayish nape, long primary extension, and a distinct pale outer edge to the outer rectrix. Note also the brighter and unbarred formative scapulars and lesser coverts. Photo by © Brad Benter

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