Further Information on the Avifauna of St. Matthew and Hall Islands, Bering Sea, Alaska

Robinson, Bryce W.; Withrow, Jack J.; Richardson, Rachel M.; Matsuoka, Steven M.; Gill, Robert E.; Johnson, Andrew S.; Lovette, Irby J.; Johnson, James A.; DeGange, Anthony R.; Romano, Marc D.

doi:10.21199/wb51.2.1

Cited by 4 publications

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“…Snow Buntings have never been documented breeding on St. Matthew Island (Winker et al 2002, Robinson et al 2020. The limited evidence for extralimital breeding by McKay's has rarely been accompanied by detailed documentation of the phenotypes involved, but phenotypic McKay's, usually males, are seen in very small numbers, less than annually, during the summer in the Pribilof Islands and on St. Lawrence Island (see Kenyon and Phillips 1965, Sealy 1967, 1969, Kessel and Gibson 1978, Lehman 2019 (Nethersole-Thompson 1966, Smith 1996, Shirihai and Svensson 2018.…”

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confidence: 99%

Plumage Variation in Bering Sea Plectrophenax Buntings and the Specific Status of McKay’s Bunting

Withrow¹

2020

WBirds

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McKay's Bunting (Plectrophenax hyperboreus) is an enigmatic and little studied passerine that breeds only on one of the most isolated groups of islands in North America. Recent field work on those islands, St. Matthew and Hall, and the nearby Pribilof Islands produced specimens of breeding McKay's and Snow Buntings (P. nivalis) demonstrating that plumage variation in both taxa is significant, probably not related to age after the first year, and varies continuously between the extremes within a taxon. The extreme of one closely approaches that of the other. McKay's Buntings are paler overall and levels of black pigmentation of the wings, back, and tail, in conjunction with sex, allow qualitative diagnosability of these taxa by plumage in nearly 100% of individuals if enough of the bird can be seen. Levels of plumage variation are congruent with recent genomic work suggesting their relationship is extremely close. Current information suggests that McKay's Bunting is not a biological species and should be considered a subspecies of the Snow Bunting. McKay's Bunting (Plectrophenax hyperboreus) is one of the least studied passerines in North America. It is endemic to the Bering Sea, breeding only on St. Matthew and Hall islands and wintering along the eastern coast of the Bering Sea (see Lyon and Montgomerie 1995). Extralimitally, it has been reported from the Chukchi and Kamchatka peninsulas (summarized

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Section: And Citations Therein)mentioning

confidence: 99%

Plumage Variation in Bering Sea Plectrophenax Buntings and the Specific Status of McKay’s Bunting

Withrow¹

2020

WBirds

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“…Under the biological species concept, geographic isolation alone, even if reinforced by differences in phenomena such as migration timing and habitat saturation, is not considered a reproductive isolating mechanism (Mayr 1996). However, this dynamic, a form of heteropatry, can be an important driver of divergence in birds (Winker 2010) and is probably operating to some extent here: Snow Buntings appear to be uncommon during spring migration at St. Matthew Island (Winker et al 2002), but they are scarce there at other times (see Robinson et al 2020). For example, in June of 2003, during transect counts of 2400 McKay's Buntings, zero Snow Buntings were identified and only five (all males) were seen off transects, the latest on 5 June (Matsuoka and Johnson 2008), suggesting that the two forms are effectively allopatric during the breeding season.…”

Section: And Citations Therein)mentioning

confidence: 99%

“…Snow Buntings have never been documented breeding on St. Matthew Island (Winker et al 2002, Robinson et al 2020. The limited evidence for VARIATION IN AND STATUS OF McKAY'S BUNTING extralimital breeding by McKay's has rarely been accompanied by detailed documentation of the phenotypes involved, but phenotypic McKay's, usually males, are seen in very small numbers, less than annually, during the summer in the Pribilof Islands and on St. Lawrence Island (see Kenyon and Phillips 1965, Sealy 1967, 1969, Kessel and Gibson 1978, S. Schuette in litt.…”

Section: And Citations Therein)mentioning

confidence: 99%

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2020

WBirds

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explores plumage variation in the buntings of the genus Plectrophenax and suggests that McKay's Bunting is a subspecies of Snow Bunting (P. nivalis) instead of a biological species. This female McKay's Bunting shows the broad white edges to the primaries, alula, and tertials, along with primary coverts that are dark for their entire length, that help to distinguish it from a male Snow Bunting at this season. On the basis of the faded primaries it may be a one-year-old bird. Note how a black and white bird can blend in well with the lichens on its preferred nesting substrate of rocky talus.

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Rapid population decline in McKay’s Bunting, an Alaskan endemic, highlights the species’ current status relative to international standards for vulnerable species

Richardson,

Amundson,

Johnson

et al. 2023

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The McKay’s Bunting (Plectrophenax hyperboreus) is endemic to Alaska, breeds solely on the remote and uninhabited St. Matthew and Hall islands (332 km2) in the central Bering Sea, and is designated as a species of high conservation concern due to its small population size and restricted range. A previous hypothesized population estimate (~2,800—6,000 individuals) was greatly increased (~31,200 individuals) after systematic surveys of the species’ entire breeding range in 2003, establishing McKay’s Bunting as one of the rarest passerines in North America. In 2018, we replicated the 2003 surveys and used density surface models to estimate breeding season densities, distributions, and population change over the intervening time period. Our results indicate that the McKay's Bunting population declined by 38% (95% CI: 27—48%) from ~31,560 to 19,481 individuals since 2003. Spatial model predictions showed no areas with an increase of birds on either St. Matthew or Hall islands but revealed declines across 13% (42 km2) of St. Matthew Island. Declines disproportionately occurred both in marginal habitats with reduced rocky nesting substrate and in high-density hotspots along the coast of St. Matthew Island. The total area occupied by breeding adults decreased by 8%, and high-density hotspots shifted inland from the coast of St. Matthew Island to higher elevations on both islands, the latter potentially responses to exceptionally warm weather and reduced spring snow cover in 2018. Additionally, we observed low numbers of predators and interspecific competitors in 2018 suggesting these did not cause the decline. Our findings indicate that McKay’s Bunting meets international standards for elevating its conservation status from Least Concern to Endangered based on the International Union for Conservation of Nature Red List of Threatened Species ranking criteria. Additional population monitoring and studies to identify the causal mechanisms of the recent population decline of this rare species could assist future population assessments.

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Further Information on the Avifauna of St. Matthew and Hall Islands, Bering Sea, Alaska

Cited by 4 publications

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Plumage Variation in Bering Sea Plectrophenax Buntings and the Specific Status of McKay’s Bunting

Plumage Variation in Bering Sea Plectrophenax Buntings and the Specific Status of McKay’s Bunting

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Rapid population decline in McKay’s Bunting, an Alaskan endemic, highlights the species’ current status relative to international standards for vulnerable species

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