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.

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Page 15 of 179

Figure 9. Variation in upperpart 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), cristatus Brown Shrike (d), and lucionensis Brown Shrike (e); see Figure 10 for underpart coloration of these same specimens. Specimen identifcation as indicated on the labels may not always be accurate, especially that between Turkestan and Isabelline Shrikes (b and c), formerly considered conspecifc. Brown Shrike subspe - cies confusus (not shown) also displays a broad range of characters, some of which are intermediate between those of cristatus and lucionensis, whereas others are not shown by either of these subspecies (see text); the warm tones to the right-hand lucionensis in these series (e) suggest that it may represent confusus. Among the specimens of Red-backed Shrike and the other taxa, a comparison with dates of collection indicates that varia - tion in reddish plumage is not attributable to specimen foxing. Photograph by Peter Pyle. 14 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 documented in other passerines (Pyle et al., in press). Among those specimens examined for this paper that were undergoing remigial molt when collected, 32 were replacing primaries bidirectionally from a medial primary, while only three specimens (Red-backed Shrikes AMNH 661056 and 661086 and Brown Shrike AMNH 661262) were replacing pri - maries distally from p1. Bidirectional replace- ment included nodes at p3 (three specimens of Turkestan Shrike), p4 (15 specimens, of all four species), and p5 (14 specimens, of all four species; see Figure 5). Secondaries are replaced bidirectionally from a node at s8 (the second tertial) and distally from a node at s1, while rectrices are replaced distally from r1 to r6 on each side of the tail, sequences that in each case are typical of passerines (Jenni and Winkler 1994; Pyle 1997, 2013a). During incomplete preforma - tive molts, most or all juvenile inner primary coverts can be retained, even in those indi - viduals that replace most or all primaries. Re- tained juvenile primary coverts appear most often to correspond to those primaries initially replaced from a central node, among p2-p7, but retention of either all or all but the outer 1-4 juvenile primary coverts was also noted on spring and summer specimens of all four species. Other retained juvenile feathers ob - served on these specimens included p1-p3, r5-r6, and up to all six secondaries among s1-s6, with proximal feathers (s5-s6) typically replaced before distal feathers (s1-s2). Reten - tion of most or all distal primary coverts, inner primaries, and outer secondaries results in an eccentric-like pattern (sensu Pyle 1997, 2008) 9b 9a

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