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 25 of 179

24 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 this paper from Europe and Asia (Alan Dean, Alexey Kryukov, Paul Leader, Evgeny Panov, Brian Small, Lars Svensson, Yoshiki Watabe, Tim Worfolk, in litt.) Assuming such hybrid parentage, careful analyses of plumage characters suggest the additional genetic infuence of Turkestan rather than Isabelline or nominate cristatus Brown Shrikes (Table 1a, Figure 12). Fea - tures less consistent with cristatus Brown Shrike than Turkestan Shrike include red - dish juvenile rectrices and bases to the in- coming outer formative rectrices (Figures 1-2, 12) and predominantly white under - parts with a rather restricted apricot-orange wash to the sides (Figures 3, 12b). Although both Red-backed and Brown Shrikes can occasionally show reddish juvenile rectrices, it seems unlikely that they would appear this richly cinnamon in a hybrid between the two. The rich, apricot-orange coloration to the sides, furthermore, is found in some proportion of both Turkestan and Isabel - line Shrikes (Dean 1982, specimen exami- nation) and is more orange-toned than the coloration seen in Red-backed and Brown Shrikes. The formative rump and upper - tail coverts also appeared to be a brighter pinkish to cinnamon rufous than the back (Figure 12a-b). Brown Shrikes, by contrast, more often show the back and rump con - colorous brown to reddish brown and the uppertail coverts brown to rufous-brown, although uncommon variants may show a brighter rump than back. Another plumage character indicating Turkestan or Isabelline Shrike as opposed to Brown Shrike introgression was the ex - tent of white in the bases of the formative primaries (Figure 13). This white patch often reaches its maximum extent on p7 or p8 (Cramp and Perrins 1993, specimen ex - amination); thus, as these feathers had not fully grown by 16 April, when the open wing of the Mendocino shrike was last pho - tographed, it is likely that the white patch would have extended even farther beyond the primary coverts once growth of the pri - maries had completed (Figures 7, 12, 13). largely white underparts with apricot-or - ange fanks and sides, and the white bases of the primaries, would also be exceptional for lucionensis (compare Figures 2, 3, and 11 with Figures 9-10), although both of these characters may sometimes be shown by some confusus (see below). Gray molting into the rump and the blackish-brown for - mative rectrices with rufous-washed bases are also inconsistent with Brown Shrike of any subspecies. Although the Mendocino shrike initially showed some features resembling lucionensis while in forma - tive plumage, the incoming frst alternate plumage, as described above, showed sub - stantial differences with this taxon. Most of the frst alternate plumage features of the Mendocino shrike at least partially matched those of Red-backed Shrike, some of them diagnostically so (Table 1a, Figures 11-12). In particular, the bright grayish head contrasting with rufous-brown back, rufous- and-white tertial edging, blackish coloration to the tail with bright white tips to the outer rectrices, and apparent white bases to some rectrices are not found in any of the other shrike taxa. However, compared with a pure Red-backed Shrike, the juvenile rectrices appeared more reddish than in most birds, the incoming formative rectrices appeared too brownish (as opposed to black), and the outer rectrices (r3-r5, at least) should have shown more-extensive white bases by the time it was last photographed (Figures 7, 11b-c). Other features that appeared to be inconsistent with a pure Red-backed Shrike included the whitish supercilium, apricot- orange tones in the sides and fanks, rather extensive white to the bases of the primaries (see below), and perhaps too little blackish on the forehead. However, all plumage fea - tures at least partially indicated Red-backed over the other shrike taxa under consider - ation, giving us confdence that the Men- docino shrike was a hybrid between Red- backed and one of the other three shrike species (Figures 11-12). An identifcation of a hybrid involving Red-backed Shrike was supported by almost all outside reviewers of Photographs taken on 4 April, with the tail partially spread, appear to show a white patch on the basal inner web of r3 (Figure 11a); otherwise, however, the bases of the formative rectrices were not extensively white as is shown in non-juvenile male Red-backed Shrikes (compare Figures 7 and 11c). By the last week of observation, incoming formative outer rectrices were chestnut to reddish, darker toward the tips; the outer two rectrices (r5 and r6) showing distinct white borders (Figure 11b, 12c-d). From below, the rectrices were pale grayish basally (translucent at certain light angles) with indistinct dusky tips (Figure 7). In Table 1a, we present differences in defnitive alternate body plumage and for - mative or basic fight feathers among males of the four species under consideration, including two subspecies of Brown Shrike, cristatus and lucionensis (subspecies confu - sus largely combines features of these other two subspecies). We also present a plumage summary of the Mendocino shrike based on descriptions and photographs taken after 5 April, when its frst alternate body plumage appearance was becoming established and its incoming formative fight-feather pat - terns could be assessed. The plumage of the Mendocino shrike does not ft a pure individual of any of the four species. The bright grayish head con - trasting distinctly with the bright reddish- brown back eliminates pure Turkestan and Isabelline shrikes, as well as the cristatus subspecies of Brown Shrike. Features that are inconsistent with lucionensis and con - fusus Brown Shrikes include the crown and back plumage mentioned above and the mixed blackish and rufous forma - tive rectrices with white tips to the outer rectrices and apparent white patches to the inner webs of others (Figure 11). No Brown Shrike shows a combination of gray - ish head and reddish-brown back; those with grayer heads (e.g., lucionensis) typi - cally show this gray more restricted to the crown and blending indistinctly with a dull brown or mud-brown nape and back. The

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