Geology topics

Rachel M. Richardson

Publications and source records attributed to Rachel M. Richardson.

3 recordsLinked to original sources

USGS2023

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

The McKay’s Bunting ( Plectrophenax hyperboreus ) is endemic to Alaska, breeds solely on the remote and uninhabited St. Matthew and Hall islands (332 km 2 ) 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 km 2 ) 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.

Alaska↗

USGS2020

Further information on the avifauna of St. Matthew and Hall Islands, Bering Sea, Alaska

In June and July 2018 and July 2019 we surveyed birds on St. Matthew and Hall islands, isolated in the central Bering Sea. Our surveys were focused on the McKay’s Bunting (Plectrophenax hyperboreus), Rock Sandpiper (Calidris ptilocnemis ptilocnemis), and Pelagic Cormorant (Phalacrocorax pelagicus) but encompassed all birds and yielded 13 species and four subspecies new to the islands’ avifaunal list, and new details and documentation of breeding for eight species. Especially notable discoveries include a mixed pair of Bewick’s (Cygnus columbianus bewickii) and Whistling (C. c. columbianus) Swans, a mixed pair of the Glaucous-winged (Larus glaucescens) and an Asian subspecies of the Herring Gull (L. argentatus vegae), and discovery of a colony of ~100 pairs of the Red-legged Kittiwake (Rissa brevirostris). Also, contrary to many previous expeditions, we found the Gray-crowned Rosy-Finch (Leucosticte tephrocotis umbrina) to be common and conclude that it may be resident.

Alaska↗

USGS2016

When winners become losers: Predicted nonlinear responses of arctic birds to increasing woody vegetation

Climate change is facilitating rapid changes in the composition and distribution of vegetation at northern latitudes, raising questions about the responses of wildlife that rely on arctic ecosystems. One widely observed change occurring in arctic tundra ecosystems is an increasing dominance of deciduous shrub vegetation. Our goals were to examine the tolerance of arctic-nesting bird species to existing gradients of vegetation along the boreal forest-tundra ecotone, to predict the abundance of species across different heights and densities of shrubs, and to identify species that will be most or least responsive to ongoing expansion of shrubs in tundra ecosystems. We conducted 1,208 point counts on 12 study blocks from 2012–2014 in northwestern Alaska, using repeated surveys to account for imperfect detection of birds. We considered the importance of shrub height, density of low and tall shrubs (i.e. shrubs >0.5 m tall), percent of ground cover attributed to shrubs (including dwarf shrubs <0.5 m tall), and percent of herbaceous plant cover in predicting bird abundance. Among 17 species considered, only gray-cheeked thrush ( Catharus minimus ) abundance was associated with the highest values of all shrub metrics in its top predictive model. All other species either declined in abundance in response to one or more shrub metrics or reached a threshold where further increases in shrubs did not contribute to greater abundance. In many instances the relationship between avian abundance and shrubs was nonlinear, with predicted abundance peaking at moderate values of the covariate, then declining at high values. In particular, a large number of species were responsive to increasing values of average shrub height with six species having highest abundance at near-zero values of shrub height and abundance of four other species decreasing once heights reached moderate values (≤ 33 cm). Our findings suggest that increases in shrub cover and density will negatively affect abundance of only a few bird species and may potentially be beneficial for many others. As shrub height increases further, however, a considerable number of tundra bird species will likely find habitat increasingly unsuitable.

Alaska↗