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 40 of 179

V O L U M E 6 9 ( 2 0 1 5 ) • N U M B E R 1 39 T H E C H A N G I N G S E A S O N S : O U T P O S T S Wood Warbler is an original "poster child" for very-long-distance vagrancy in the context of ap - parent reverse migration. In the twentieth centu- ry, the species was thought to breed only in Eu- rope west of the Urals and to winter in tropical Africa. In recent years, multiple autumn records have accumulated for Japan and western Alaska, and we now know that its breeding range actu - ally extends farther to the east, to the Ob' River region in central Russia. Nevertheless, that area is still at least 4800 kilometers from the Aleu - tians and Bering Sea islands, where in autumn 2014 a single Wood Warbler was found at Adak Island, a frst for the central Aleutians (Figures 2, 3), and two were discovered at St. Paul (where there is one previous record)—thus doubling the previous number of North American re - cords. Even more amazing was the fourth Wood Warbler of the 2014 season found an additional several hundred kilometers east, on Middleton Island in the Gulf of Alaska. Most of the Alaskan records of Wood Warbler are from early October. Autumn Vagrancy in western Alaska The potential of discovering such long-distance strays as Wood Warbler is clearly what attracts most visiting birders to the western Alaska is - lands in fall, and fall has indeed proven to be a very productive period for such vagrants, though their appearances are irregular. The fall of 2014 was excellent for such species in the Bering Sea region. Highlights during the season at St. Paul included Garganey, Common Pochard, four Jack Snipe, Willow Warbler, Common Chiffchaff, two Red-fanked Bluetails, Taiga Flycatcher (Figure 4), and Dusky Thrush. On St. Lawrence Island, Asian birds found at Gambell included a Tundra/ Taiga Bean-Goose, Eurasian Hobby, two Brown Shrikes, two Willow Warblers (Figure 5), two Yellow-browed Warblers, Red-fanked Bluetail, and two Tree Pipits (Figure 6). Much improved autumn coverage since the late 1990s at Gambell and St. Paul has shown that perhaps even more surprising than the (mostly, but far from entirely, predicted) Asian strays has been the regular fnding of North American mainland strays, many of which are even farther out of range. Almost all of these latter birds ft the reverse-migrant model as well. In autumn 2014, for example, single Least Flycatchers and Mourning Warblers at Gambell were not even autumn frsts for that site, whereas a Red-eyed Vireo there was a frst for the Bering Sea region, and a Northern Mockingbird was truly bizarre (though actually the second offshore Bering Sea record). At St. Paul, a Sharp-shinned Hawk was an offshore Bering Sea frst. But all of those were outdone by the on-nobody's-radar-list Wood Thrush at St. Paul, a frst for Alaska (Figures 7, 8). If a Lesser Nighthawk can be found at the mouth of the Noatak River north of Kotzebue (August 1985) or a Kentucky Warbler can turn up at the Arctic National Wildlife Refuge on the North Slope (September 1982), then the pos - sibilities seem almost endless for misoriented migrants in the Far North. The pool of potential vagrants to any region of North America (or Europe) is large and in - cludes a substantial array of mostly long-dis- tance migrants from a variety of regions. The limits of what may occur are mostly determined by length of normal migration route, survival over large water crossings, and survival of in - sectivores that encounter cold temperatures and a lack of suffcient food. Productive vagrant searching through mid-October has been known since the late 1970s on the western Aleutian Is - lands. But at such other western Alaska sites as Gambell and St. Paul, birder activity until very recently waned by the beginning of October, perhaps due to the belief that the onset of ever- colder temperatures in interior Russia and Alas - ka would preclude additional half-hardy species from surviving the long journey. But recent addi - tional coverage through the frst half of October at St. Paul and at Gambell is showing that this is not the case. It remains to be seen how late into the fall such reverse migrants and random wan - derers might still occur at sites scattered across much of northern Alaska and Arctic Canada. No doubt there have been major advances in our knowledge of the status and distribution of birds, in our understanding of vagrant birds, in our ability to forecast weather events and to Figures 7, 8. Thousands of kilometers from its nearest nesting areas and in a bizarre biome for the species, Alaska's frst Wood Thrush fed along the roads of St. Paul Island 3 October 2014. This may be the most surprising rarity ever to have reached the Pribilofs. Photographs by Scott Schuette. Figure 9. This Yellow-browed Warbler in the Middleton Island thickets 19 September 2014 represents the third species of Phylloscopus recorded at that remote island in the Gulf of Alaska and Alaska's frst Yellow-browed away from the Bering Sea/ Aleutian Islands outposts. Photograph by Nicholas R. Hajdukovich.

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