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 30 of 179

Figure 17. Projected range of migratory pathways for shrikes assuming reverse migration (see Howell et al. 2014) and based on projected breeding and winter ranges. Black lines indicate the range of potential vectors given breeding and winter ranges, red lines indicate the mid- point, and concentric gray rings indicate 1000 km distances from the centers of hybridization zones and subspecies ranges. Shown are 180º misorientation projections based on the Red-backed/Turkestan Shrike hybridization zone (a), the Red-backed/Brown Shrike hybridization zone (b), the range of cristatus Brown Shrike (c), and the range of lucionensis Brown Shrike (d). See text for discussion. Graphics by Shane Feirer. Figure 18. Presumed Turkestan x Red-backed Shrike hybrids photographed in Saudi Arabia (Babbington 2013, 2014) on 27 April 2013 (a, b) and 13 April 2014 (d, c). Note the similarities between the plumage of these birds and the Mendocino shrike, including indistinct whitish supercilia, rufous or mixed rufous-and-gray uppertail coverts contrasting with browner backs, rufous bases to the outer rectrices, whitish underparts with pinkish to apricot sides and fanks, and white extending beyond the primary coverts. Note also that tail morphology of these hybrids (b, c) is similar to that of the Mendocino Shrike (Figure 15b, c) and would be expected of Red-backed x Turkestan hybrids (Table 1b); the ratio c/d was calculated as 0.118 (image b) and 0.132 (image c). Photographs by Jahed Alammadi (a, b) and Jem Babbington (d, c). 29 V O L U M E 6 9 ( 2 0 1 5 ) • N U M B E R 1 T H E M E N D O C I N O S H R I K E Shrikes, falling 7-14 mm short of the tail tip and roughly equal in width with the other rectrices, whereas in all subspecies of Brown Shrike, r6 is substantially shorter, falling 14-27 mm short of the tail tip, and also averaging over 1 mm nar - rower than the other rectrices (Svensson 1992, Cramp and Perrins 1993; Figure 14). On non-molting birds in the hand, feathers can be compared directly and distances between tips measured to separate these taxa, but obtain - ing such specifc biometrics is not possible with images of the Mendocino shrike due to feather positions, camera angles, and the fact that it was molting critical primaries (p3-p6) and rectrices (r1-r2) by the time adequate images could be ob - tained to evaluate structural morphology. Most reviewers of the images thought that both the juvenile p9 and the juvenile outer rectrix (r6), prior to these feathers molting, looked too long for a Brown Shrike, and that r6 looked roughly equal in width to other un-molted rectrices. In order to confrm these impressions and to assess wing and tail structure as related to the identi - fcation of the Mendocino shrike, Pyle obtained biometrics from specimens to calculate ratios between feather tips that could be applied to the same ratios in the images. This process carries the assumption that ratios will be less affected by angle of the feather tract relative to the plane of the image than are estimated biometrics. Primary and rectrix morphology ratios could not be applied to the newer formative feathers of the Mendocino shrike, as the outer primaries and rectrices were not fully grown when it was last observed (Figures 7, 13), so ratios were based on its juvenile feathers. The outer three juvenile primaries (p8-p10) were present (had not yet molted) in photographs up through at least 4 April, and the outer two juvenile rectrices (r5-r6) were present until 31 March, so ratios between these feather tips were used in images taken through these dates (Figure 15, Table 1b). The distances between p8 and p9 (a) and p9 and the primary coverts (b) were measured in specimens in order to calculate the ratio a/b and apply it to images showing these feathers. The upperwing and underwing primary coverts Brown Shrike, especially for a male. Moreover, frst-year male Brown Shrikes typically show a gray-based lower mandible that becomes black by April, rather than a pinkish base as shown through mid-April by the Mendocino shrike. Red-backed Shrikes average longer wing lengths than Turkestan and Isabelline Shrikes, which in turn average longer wings and great - er primary projections than any of the Brown Shrike taxa (Svensson 1992, Cramp and Per - rins 1993). On the other hand, Brown Shrikes average slightly longer tails than Turkestan and Isabelline Shrikes, which in turn average longer tails than Red-backed Shrike. Wing-to-tail ra - tios can be useful in the hand but, unfortunately, are nearly impossible to determine with conf - dence in photographs due to uncertain angles of orientation to feather tracts relative to the plane of an image. Comments from those familiar with the identifcation of these shrikes indicated that the primary projection of the Mendocino shrike appeared to be too short for Red-backed Shrike but too long for most Brown Shrikes and that the tail appeared too long for Red-backed Shrike but too short for Brown Shrike. Relative wing and tail proportions are also affected by camera angle, bird posture, and the fact that the Men - docino shrike was molting both primaries and rectrices during the period of observation. Primary and rectrix morphologies, the rela - tive distances between the tips of certain feath- ers within each of these tracts, differ fairly substantially among shrikes in this assemblage (Dement'ev and Gladkov 1954, Dean 1982, Svensson 1992, Cramp and Perrins 1993, Wor - folk 2000; Figure 14). The penultimate primary (p9) is longest in Red-backed Shrike, falling 3-9 mm short of the wing tip and equidistant to the tips of p6-p7 inclusive (Svensson 1992, Cramp and Perrins 1993); it is a bit shorter in Turke - stan Shrike and migratory nominate Isabelline Shrike (5-9 mm short of the wing tip and equal to p5-p6); and it is shortest in the Brown Shrikes, including nominate cristatus (6-12 mm short of the wing tip and equal to p4-p5). Likewise, the outer rectrix (r6) is relatively long and wide in Red-backed, Turkestan, and nominate Isabelline 18a 18b 18c 18d c d c d c c d c

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