• Reproductive success of American and Pacific golden-plovers (Pluvialis dominica and P. fulva) in a changing climate

      Overduijn, Kelly S.; Powell, Abby N.; Handel, Colleen M.; Sikes, Derek (2019-05)
      Climate change is increasing air temperatures and altering hydrologic systems in arctic environments, which will create positive feedbacks on shrub growth and advance the phenology of arthropods, important prey for many Arctic-breeding birds. Little is understood about how such climate-induced changes in habitat and prey availability may affect reproductive success of migratory birds during the short arctic breeding season. Worldwide, declines in shorebird populations, including arctic-breeding species, have recently become apparent. Projected changes in climate are expected to benefit Arctic-breeding shorebirds in the short-term by increasing reproductive success and survival, primarily through prolongation of summer. Over time, however, reductions in the quantity and quality of open tundra habitat and changes in prey availability may adversely affect shorebird reproduction and exacerbate current population declines. I evaluated the reproductive success of two shorebird species, American (Pluvialis dominica) and Pacific (P. fulva) Golden-Plovers, in relation to vegetation extent and phenology. I collected data over two field seasons (2012-2013) on the Seward Peninsula, Alaska. Both species selected nest sites with less cover of tall shrubs and other tall vegetation than available at random sites within their territories. American Golden-Plovers selected territories and nest sites that were higher in elevation and had more rocky substrates and less graminoid vegetation than those selected by Pacific Golden-Plovers. Nest survival was equivalent in the two species and similar to that found in other arctic-breeding shorebirds. Over the 27-d incubation period the probability of a nest having at least one egg survive to hatch averaged 0.39 (95% CI: 0.28, 0.49). Nest survival was not explicitly associated with habitat features at nest sites; however, nest survival was lower during the year with earlier spring phenology and declined with the age of the nest, both of which may have been at least partially related to growth of vegetation. Future research should examine reproductive success in a comprehensive manner, in which multiple aspects of a species' reproductive ecology is evaluated, allowing a more complete understanding of the effects of climate change on recruitment into populations through the combined effects of habitat structure, food resources, and climate.
    • Speciation genetics in two pairs of high-latitude, migratory bird taxa

      Withrow, Jack J.; Winker, Kevin; Hundertmark, Kris; Takebayashi, Naoki (2013-05)
      I investigated and characterized the divergence of two pairs of putatively young, high-latitude, migratory bird taxa with data from mitochondria) and nuclear DNA. I chose pairs exhibiting natural history attributes suggesting divergence scenarios that probably did not involve strict allopatry. First, I examined Pluvialis dominica and P. fulva, migratory plover species with a largely parapatric breeding range in Beringia. Secondly, I examined Aegolius acadicus acadicus and A. a. brooksi, a subspecies pair of owls where one subspecies (brooksi) is endemic to Haida Gwaii, Canada, a location where subspecies acadicus occurs during migration, resulting in cyclic sympatry (heteropatry) with brooksi. Using mtDNA sequence data and AFLPs I made inferences about population parameters, inferred the likely number of populations, and sought evidence of selection. Gene flow was very low in both pairs. The plovers are much older than was anticipated (1.8 Mybp), although hybridization does occur. Evidence for parapatric or speciation with gene flow scenarios was not found in the plovers, perhaps because the speciation event occurred far in the past. The owl's divergence date was relatively young (~16,000 ybp). Some evidence was found suggesting that heteropatric divergence contributed to the owl's differentiation, although the process could also have reinforced differences acquired largely in allopatry.