North American Birds

VOLUME 69 No1 2016

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/629070

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16 N O R T H A M E R I C A N B I R D S T H E M E N D O C I N O S H R I K E mer and late winter, show worn fight feathers typical of those not replaced for nearly a year, or else show apparent suspensions indicating a single long protracted molt. A careful read - ing of both Medway (1970) and Stresemann and Stresemann (1971), furthermore, indi - cates little evidence for two molts per year and some evidence (e.g., very worn feathers being replaced in spring, fresh non-molting birds in April, and spring molts proceeding distally from medial primaries after suspen - sions), suggesting single variable fight-feather molts, as has been documented in Red-backed Shrike (Snow 1965) and Turkestan and Isa - belline Shrikes (Stresemann and Stresemann 1972). We would consider it unusual for two complete molts per year to be confned to one taxon within the Red-backed/Turkestan/ Isabelline/Brown shrike species assemblage. The above conclusions on molt in the Brown Shrike were arrived at independent of those of Neufeldt (1978, summarized by Panov et al. 2011: 71-73), who came to several similar suppositions. Specimen examination other - wise revealed few differences in molt strategies among the taxa considered for the Mendocino shrike, differences in timing and extents de - pending more on migratory status and winter- ing latitude of the individual. Most frst-year individuals of this shrike species assemblage can be aged by the reten - tion of brown and worn juvenile primary co- verts, with one to fve distal feathers replaced. Juvenile outer primaries and rectrices are also narrower and more worn as compared to for - mative and defnitive basic feathers, and these differences can be used to age molting individ - uals and those that do not undergo complete fight-feather molt (Svensson 1992, Jenni and Winkler 1994). Further investigation may be needed to determine what proportion of these shrikes, especially Red-backed Shrikes, may undergo a complete preformative molt (in - cluding all primary coverts), as these appear not to be reliably separated from older adults in spring and summer. Careful analysis by Pyle of dozens of im - Figure 10. Variation in underpart coloration of alternate- plumaged males among specimens at AMNH identifed as fve taxa considered for the Mendocino shrike: Red-backed Shrike (a), Turkestan Shrike (b), Isabelline Shrike (c), crista - tus Brown Shrike (d), and lucionensis Brown Shrike (e); see Figure 9 for comments on the identifcation of these speci - mens and on Brown Shrike subspecies confusus. All varia- tion among certain taxa is not captured in these images; in particular, many male Turkestan and Red-backed Shrikes show brighter apricot-orange sides than are captured here. Photograph by Peter Pyle. 10a 10b

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