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

Contents of this Issue

Navigation

Page 33 of 179

c d c d 32 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 itself over the Pacifc Ocean, as predicted by the midpoint of such trajectories, and continued on or drifted to reach the closest point of coastal land, as has been proposed for both North American and Asian vagrants that reach the Pacifc North American coast (Howell et al. 2014). The same calculations applied to a prospec- tive Red-backed x Brown Shrike hybrid re- sults in a 180º misorientation trajectory more westward in the Pacifc (Figure 17b) than the projected path of a Red-backed x Turkestan Shrike hybrid, although the same possibility mentioned above may apply to a Red-backed x Brown Shrike hybrid that fnds itself over the Pacifc Ocean fying or drifting until it makes landfall. Distance traveled would also be slightly longer to reach Mendocino County (8000-9000 km) than it would be to reach prospective wintering grounds for such a hy - Figure 21. Specimen of a presumed male Red-backed x Brown Shrike hybrid collected in the zone of sympatry between the two species, in the Kuznetsk Alatau range of Russia, on 10 July 1983, after having raised young with a female Red-backed Shrike (see Kryukov and Gureev 1997; specimen at the Zoologi- cal Institute, Russian Academy of Sciences, Saint Petersburg, Russia). Although superfcially resembling the Mendocino shrike, note diferences summarized in Figure 20. The ratio of c/d for this specimen's tail morphology (see Figures 15, 18-20) is 0.161, well above the ratios calculated for the Mendocino shrike (Table 1b). Photographs by Alexey P. Kryukov. 21a 21b 21c brid (6000-8000 km; Figure 17b). These 180º misorientation calculations applied to crista - tus Brown Shrike show how this subspecies might be expected throughout most of North America, including Nova Scotia, with the mid - line of these pathways directing birds close to the California coast (Figure 17c), and distance traveled being about the same (5000-7000 km) in each direction. On the other hand, a lu - cionensis Brown Shrike, based on a maximum normal migratory distance of about 4500 km, would result in destination end-points throughout northern Russia east to the tip of Siberia, and some 3500-4500 km from the California coast (Figure 17d). Many caveats need to be applied to vagrancy theories, how - ever, with some vagrants defying these sort of calculations and others affected by weather systems, disorientation, and other vagrancy mechanisms (Howell et al. 2014). Comparison with other hybrid shrikes We have established that the Mendocino shrike was a hybrid involving Red-backed Shrike and one or more of Turkestan, Isabel - line, and/or nominate cristatus Brown Shrikes. In this section, we compare the plumage and morphology of the Mendocino shrike with those of other reported hybrids. We examined photographs in the literature and online of 34 male shrikes reported to be hybrids, not in - cluding those shown in Figures 17.1 and 17.7 of Panov et al. (2011). Twenty-eight of these reported hybrids were photographed in Kazakhstan and countries of the Arabian Peninsula (e.g., Babbington 2013, 2014; Figures 18a-b) and were identifed as or showed characters of Red-backed x Turke - stan Shrike hybrids. These 28 hybrids display substantial variation in plumage, from those resembling Red-backed Shrike with a slight red tinge to the bases of the outer rectrices to those resembling Turkestan Shrikes with a slight grayish tinge to the crown and a dusky wash to the central rectrices. Most showed tail patterns resembling that of the Mendocino Shrike, with brownish-black central rectrices, a duskier subterminal band, variably rufous to cinnamon-whitish bases to the outer four pairs of rectrices, and whitish to white tips to the outermost rectrices. The range of plumage variation shown by these 28 hybrid shrikes is consistent with a broad zone of genetic in - trogression as has been documented to occur between Red-backed and Turkestan Shrikes (Panov et al. 2011). Many of these 28 presumed Red-backed x Turkestan Shrike hybrids, including those photographed in Saudi Arabia and shown in Figure 18, resemble the Mendocino shrike in most or all plumage features. In addition to the pattern of the rectrices, notable similari - ties to the Mendocino shrike shown by these hybrids include an indistinct whitish supercil - ium, rufous or mixed rufous-and-gray rump and uppertail coverts contrasting with brown - er back, largely white underparts with pinkish to apricot-orange wash in the sides and fanks, and white extending beyond the primary co -

Articles in this issue

Archives of this issue

view archives of North American Birds - VOLUME 69 No1 2016