North American Birds

VOLUME 69 NO2 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/705084

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Figure 4. Weather map for the north Pacific showing weather systems and their projected tracks at 0400 HADT, 6 October 2013. Map courtesy of the Ocean Prediction Center, National Weather Service, National Oceanic and Atmospheric Administration. Figure 5. Weather map for the North Pacific showing weather systems and their projected tracks at 1600 HADT, 7 October 2013. Map courtesy of the Ocean Prediction Center, National Weather Service, National Oceanic and Atmospheric Administration. 188 N O R T H A M E R I C A N B I R D S C O M M O N R E D S TA R T O N S T. PA U L I S L A N D, A K pers. comm.). Both subspecies show pale edges to most or all of the secondaries when in fresh plumage, but in Ehrenberg's, this pale is usually stark white, rather than buffy, and it bleeds extensively into the outer webs, es - pecially towards the bases. In the upperparts, Ehrenberg's shows gray feathers fringed with brown, especially in the lower mantle, while nominate phoenicurus shows mostly or all brown feathering above. In specimens, this aspect of the upperparts varies more than the differentiating characteristics of the remiges (Small 2009). Although the St. Paul bird did show obvi - ous pale fringes to the tertials and inner sec- ondaries, and thinner ones towards the outer secondaries (Figures 1, 2), these fringes were obviously buffy, rather than white, and this edging did not expand towards the bases of the feathers (on two of the tertials it actually appears to get thinner towards the bases of the feathers). Dorsally, it also appeared mostly dull brownish, without much gray showing through on the mantle. We conclude that these characteristics identify the St. Paul red - start as a Common Redstart (Phoenicurus phoe- nicurus) of the nominate subspecies. Discussion The occurrence of vagrant landbirds from Eurasia in the Pribilof Islands, and elsewhere in western Alaska as well as North America as a whole, is often dependent on the weather systems that pass eastward across the Bering Sea and North Pacific regions. During the fall of 2013, the jet stream was located over the southern Bering Sea for an extended period, which allowed these systems to pass both to the north and south of the Aleutian Islands and provided the Pribilofs with a series of strong to moderately strong storms during the months of September and October. The weather preceding this sighting in - cluded the passage of a powerful low-pressure system that moved offshore into the Sea of Okhotsk 3 October, where it dissipated as another weak low-pressure system passed northwestward along the coast of the Kam - chatka Peninsula toward the Gulf of Anadyr (Figure 3). The westerlies along the southern edge of the first system funneled into the west - ern edge of the second system which slowly made its way northward, stalling along the Russian coastline just south of the Gulf of Anadyr 5 October (Figure 4). The second system controlled the weather to its south as far as southern Kamchatka beginning 4 Oc - tober, with the leading edge of the southeast- ern portion of the system reaching St. Paul inner secondaries, sometimes tipped with a variable amount of buff when fresh. In the outer tertials, and inner secondaries, this white fringe widens towards the feather bases, so the extent of white is noticeably greater to - wards the bases of the feathers than toward the tips. The outer secondaries show less ex - tensive pale buff or creamy-white edges. On the folded wing, this pattern gives the effect of a narrow white triangle on the outer tertials and inner secondaries, narrowing towards the wingtip (Small 2009; M. Crewe, B. Small, Redstart—breeds in eastern Turkey, the Cau - casus, and the Middle East (Small 2009). Both subspecies winter in Arabia and sub-Saharan Africa (Christie 2013). In first-winter birds, these subspecies dif - fer in the extent and character of pale fringing on the tertials and secondaries, the upperparts coloration, and the voice (Small et al. 2009, Svensson et al. 2010; M. Crewe, B. Small, K. Mullarney, pers. comm.). Hatch-year male Ehrenberg's Redstarts show narrow white edges to the tertials and

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