Browsing by Author "Kwon, Eunbi"

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    Composition and Drivers of Gut Microbial Communities in Arctic-Breeding Shorebirds
    Grond, Kirsten; Santo Domingo, Jorge W.; Lanctot, Richard B.; Jumpponen, Ari; Bentzen, Rebecca L.; Boldenow, Megan L.; Brown, Stephen C.; Casler, Bruce; Cunningham, Jenny A.; Doll, Andrew C.; Freeman, Scott; Hill, Brooke L.; Kendall, Steven J.; Kwon, Eunbi; Liebezeit, Joseph R.; Pirie-Dominix, Lisa; Rausch, Jennie; Sandercock, Brett K. (2019-10-09)
    Gut microbiota can have important effects on host health, but explanatory factors and pathways that determine gut microbial composition can differ among host lineages. In mammals, host phylogeny is one of the main drivers of gut microbiota, a result of vertical transfer of microbiota during birth. In birds, it is less clear what the drivers might be, but both phylogeny and environmental factors may play a role. We investigated host and environmental factors that underlie variation in gut microbiota composition in eight species of migratory shorebirds. We characterized bacterial communities from 375 fecal samples collected from adults of eight shorebird species captured at a network of nine breeding sites in the Arctic and sub-Arctic ecoregions of North America, by sequencing the V4 region of the bacterial 16S ribosomal RNA gene. Firmicutes (55.4%), Proteobacteria (13.8%), Fusobacteria (10.2%), and Bacteroidetes (8.1%) dominated the gut microbiota of adult shorebirds. Breeding location was the main driver of variation in gut microbiota of breeding shorebirds (R-2 = 11.6%), followed by shorebird host species (R-2 = 1.8%), and sampling year (R-2 = 0.9%), but most variation remained unexplained. Site variation resulted from differences in the core bacterial taxa, whereas rare, lowabundance bacteria drove host species variation. Our study is the first to highlight a greater importance of local environment than phylogeny as a driver of gut microbiota composition in wild, migratory birds under natural conditions.
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    Contrasting long-term population trends of beach-nesting shorebirds under shared environmental pressures
    Kwon, Eunbi; Robinson, Samantha G.; Weithman, Chelsea E.; Catlin, Daniel H.; Karpanty, Sarah M.; Altman, Jon; Simons, Theodore R.; Fraser, James D. (Elsevier, 2021-08-01)
    Identifying the drivers of long-term population change is a key goal of ecological studies. It is complicated by extrinsic and intrinsic factors that may covary with time and/or operate on a time lag. For migratory shorebirds that breed on the barrier islands of eastern North America, populations may be limited by the anthropogenic, climatic, biological environments they encounter throughout the annual cycle. Using three-decades (1989–2017) of breeding monitoring data collected by the National Park Service at two national seashores in North Carolina (Hatteras and Lookout), we examined the potential drivers of nesting piping plover (Charadrius melodus) and American oystercatcher (Haematopus palliates) populations. Hatteras had five times more annual visitors than Lookout, and our modelling revealed a strong negative relationship between the population size of breeding plovers and human activity and a positive relationship with protection efforts aimed at reducing disturbance. Breeding and wintering climatic conditions, population productivity, and nesting habitat availability showed only weak effects. Thus, a decade-long decline in plover numbers at both seashores starting in the mid-90s reversed as the parks' visitor counts decreased and stricter protections from potential disturbance were implemented. However, the two sympatric populations of oystercatchers showed the opposite population trends from each other at the neighboring seashores, increasing only on Lookout after a hurricane improved habitat and subsequently the reproductive output. Our study suggests a strong relationship between the anthropogenic environment and the population trend of a threatened species and, simultaneously, the important role of stochastic events in shaping populations of long-lived shorebird species.
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    Delayed egg-laying and shortened incubation duration of Arctic-breeding shorebirds coincide with climate cooling
    Kwon, Eunbi; English, Willow B.; Weiser, Emily L.; Franks, Samantha E.; Hodkinson, David J.; Lank, David B.; Sandercock, Brett K. (Wiley, 2017)
    Biological impacts of climate change are exemplified by shifts in phenology. As the timing of breeding advances, the within-season relationships between timing of breeding and reproductive traits may change and cause long-term changes in the population mean value of reproductive traits. We investigated long-term changes in the timing of breeding and within-season patterns of clutch size, egg volume, incubation duration, and daily nest survival of three shorebird species between two decades. Based on previously known within-season patterns and assuming a warming trend, we hypothesized that the timing of clutch initiation would advance between decades and would be coupled with increases in mean clutch size, egg volume, and daily nest survival rate. We monitored 1,378 nests of western sandpipers, semipalmated sandpipers, and red-necked phalaropes at a subarctic site during 1993–1996 and 2010–2014. Sandpipers have biparental incubation, whereas phalaropes have uniparental incubation. We found an unexpected long-term cooling trend during the early part of the breeding season. Three species delayed clutch initiation by 5 days in the 2010s relative to the 1990s. Clutch size and daily nest survival showed strong within-season declines in sandpipers, but not in phalaropes. Egg volume showed strong within-season declines in one species of sandpiper, but increased in phalaropes. Despite the within-season patterns in traits and shifts in phenology, clutch size, egg volume, and daily nest survival were similar between decades. In contrast, incubation duration did not show within-season variation, but decreased by 2 days in sandpipers and increased by 2 days in phalaropes. Shorebirds demonstrated variable breeding phenology and incubation duration in relation to climate cooling, but little change in nonphenological components of traits. Our results indicate that the breeding phenology of shorebirds is closely associated with the temperature conditions on breeding ground, the effects of which can vary among reproductive traits and among sympatric species.
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    Effects of environmental conditions on reproductive effort and nest success of Arctic-breeding shorebirds
    Weiser, Emily L.; Brown, Stephen C.; Lanctot, Richard B.; Gates, H. River; Abraham, Kenneth F.; Bentzen, Rebecca L.; Bety, Joel; Boldenow, Megan L.; Brook, Rodney W.; Donnelly, Tyrone F.; English, Willow B.; Flemming, Scott A.; Franks, Samantha E.; Gilchrist, H. Grant; Giroux, Marie-Andree; Johnson, Andrew; Kendall, Steven J.; Kennedy, Lisa V.; Koloski, Laura; Kwon, Eunbi; Lamarre, Jean-Francois; Lank, David B.; Latty, Christopher J.; Lecomte, Nicolas; Liebezeit, Joseph R.; McKinnon, Laura; Nol, Erica; Perz, Johanna; Rausch, Jennie; Robards, Martin; Saalfeld, Sarah T.; Senner, Nathan R.; Smith, Paul A.; Soloviev, Mikhail; Solovyeva, Diana; Ward, David H.; Woodard, Paul F.; Sandercock, Brett K. (2018-07)
    The Arctic is experiencing rapidly warming conditions, increasing predator abundance, and diminishing population cycles of keystone species such as lemmings. However, it is still not known how many Arctic animals will respond to a changing climate with altered trophic interactions. We studied clutch size, incubation duration and nest survival of 17 taxa of Arctic-breeding shorebirds at 16 field sites over 7years. We predicted that physiological benefits of higher temperatures and earlier snowmelt would increase reproductive effort and nest survival, and we expected increasing predator abundance and decreasing abundance of alternative prey (arvicoline rodents) to have a negative effect on reproduction. Although we observed wide ranges of conditions during our study, we found no effects of covariates on reproductive traits in 12 of 17 taxa. In the remaining taxa, most relationships agreed with our predictions. Earlier snowmelt increased the probability of laying a full clutch from 0.61 to 0.91 for Western Sandpipers, and shortened incubation by 1.42days for arcticola Dunlin and 0.77days for Red Phalaropes. Higher temperatures increased the probability of a full clutch from 0.60 to 0.93 for Western Sandpipers and from 0.76 to 0.97 for Red-necked Phalaropes, and increased daily nest survival rates from 0.9634 to 0.9890 for Semipalmated Sandpipers and 0.9546 to 0.9880 for Western Sandpipers. Higher abundance of predators (foxes) reduced daily nest survival rates only in Western Sandpipers (0.9821-0.9031). In contrast to our predictions, the probability of a full clutch was lowest (0.83) for Semipalmated Sandpipers at moderate abundance of alternative prey, rather than low abundance (0.90). Our findings suggest that in the short-term, climate warming may have neutral or positive effects on the nesting cycle of most Arctic-breeding shorebirds.
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    Effects of leg flags on nest survival of four species of Arctic-breeding shorebirds
    Weiser, Emily L.; Lanctot, Richard B.; Brown, Stephen C.; Gates, H. River; Bentzen, Rebecca L.; Boldenow, Megan L.; Cunningham, Jenny A.; Doll, Andrew C.; Donnelly, Tyrone F.; English, Willow B.; Franks, Samantha E.; Grond, Kirsten; Herzog, Patrick; Hill, Brooke L.; Kendall, Steven J.; Kwon, Eunbi; Lank, David B.; Liebezeit, Joseph R.; Rausch, Jennie; Saalfeld, Sarah T.; Taylor, Audrey R.; Ward, David H.; Woodard, Paul F.; Sandercock, Brett K. (2018-09)
    Marking wild birds is an integral part of many field studies. However, if marks affect the vital rates or behavior of marked individuals, any conclusions reached by a study might be biased relative to the general population. Leg bands have rarely been found to have negative effects on birds and are frequently used to mark individuals. Leg flags, which are larger, heavier, and might produce more drag than bands, are commonly used on shorebirds and can help improve resighting rates. However, no one to date has assessed the possible effects of leg flags on the demographic performance of shorebirds. At seven sites in Arctic Alaska and western Canada, we marked individuals and monitored nest survival of four species of Arctic-breeding shorebirds, including Semipalmated Sandpipers (Calidris pusilla), Western Sandpipers (C. mauri), Red-necked Phalaropes (Phalarope lobatus), and Red Phalaropes (P. fielicarius). We used a daily nest survival model in a Bayesian framework to test for effects of leg flags, relative to birds with only bands, on daily survival rates of 1952 nests. We found no evidence of a difference in nest survival between birds with flags and those with only bands. Our results suggest, therefore, that leg flags have little effect on the nest success of Arctic-breeding sandpipers and phalaropes. Additional studies are needed, however, to evaluate the possible effects of flags on shorebirds that use other habitats and on survival rates of adults and chicks.