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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11b 11c 11a T H E M E N D O C I N O S H R I K E 18 N O R T H A M E R I C A N B I R D S Figure 11. The Mendocino Shrike on 4 April (a) and 16 April (b), showing characters indicative or diagnostic of Red-backed Shrike among the six taxa under consider - ation (Table 1; see text). The appar- ent white patch to the inner web of r3 (a) was noted on images taken by diferent observers, and close examination of the images further suggests that it is not a photo- graphic artifact. No other images taken subsequent to this shows the inner webs of these rectrices from above, while images from below (e.g., Figure 7) might not be ex- pected to show the same pattern. Several features of the Mendocino shrike, however, do not indicate a pure Red-backed Shrike including, notably, reddish-brown alternate feathers in the hindcrown (a) and the lack of more-extensive white bases to r3-r5, as typically found in this species (c; MVZ 21374); see also Figure 7. Photographs by Gary Woods (a), Richard Hubacek (b), Peter Pyle (c). Table 1. Plumage (a) and structural morphological (b) characters of the Mendocino shrike along with those for fve taxa under consideration for its identifcation. Plumage characters and biometrics were derived from descriptions and images for the Mendocino shrike as compared to the literature and specimen examination for alternate-plumaged males of the fve contending taxa. Analyses of morphological ratios in specimens of males with juvenile, formative, and basic outer primaries and rectrices yielded no signifcant efects of age or feather generations, so ages were lumped in calculating the ratios from specimens. See text for details. For Isabelline Shrike, it is possible that some of the specimens were of sub- species arenarius or tsaidemensis, misidentifed as isabellinus, which may have resulted in shorter wing and tail morphologies than is true of isabel- linus ; isabellinus likely should match phoenicuroides more closely in wing and tail structure (Svensson 1992; L. Svensson, pers. comm.). Not enough Brown Shrike specimens confrmed to subspecies confusus were avail- able to include in this table; see text for discussion of plumage features, largely intermediate between cristatus and lucionensis. Reddish-brown crown feathers Rufous and white edging to tertials Distinct crown-back contrast White patch at base of growing r3 lower back and pale brown Mixed grayish Mixed grayish and pale brown lower back to r5 and r6 White tips White tips to r5 and r6

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