Anas Laysanensis Research Articles

Feather corticosterone is lower in translocated and historical populations of the endangered Laysan duck (Anas laysanensis).

Identifying reliable bioindicators of population status is a central goal of conservation physiology. Physiological stress measures are often used as metrics of individual health and can assist in managing endangered species if linked to fitness traits. We analysed feather corticosterone, a cumulative physiological stress metric, of individuals from historical, translocated, and source populations of an endangered endemic Hawaiian bird, the Laysan duck (Anas laysanensis). We hypothesized that feather corticosterone would reflect the improved reproduction and survival rates observed in populations translocated to Midway and Kure Atolls from Laysan Island. We also predicted less physiological stress in historical Laysan birds collected before ecological conditions deteriorated and the population bottleneck. All hypotheses were supported: we found lower feather corticosterone in the translocated populations and historical samples than in those from recent Laysan samples. This suggests that current Laysan birds are experiencing greater physiological stress than historical Laysan and recently translocated birds. Our initial analysis suggests that feather corticosterone may be an indicator of population status and could be used as a non-invasive physiological monitoring tool for this species with further validation. Furthermore, these preliminary results, combined with published demographic data, suggest that current Laysan conditions may not be optimal for this species.

Avian botulism is a primary, year-round threat to adult survival in the endangered Hawaiian Duck on Kaua‘i, Hawai‘i, USA

AbstractAdult survival is the most important demographic parameter influencing population dynamics for many bird taxa. Thus, understanding how survival probabilities and causes of mortality vary throughout the annual cycle is critical for developing informed and effective management strategies. In this study, we used radio-telemetry data to evaluate the effects of biotic (e.g., sex, peak [September–April] vs. off-peak [May–August] nesting seasons) and abiotic factors (e.g., rainfall, year, bi-monthly interval) on adult survival, estimate annual survival probabilities, and identify primary sources of mortality for Hawaiian Ducks (Anas wyvilliana), an endangered, non-migratory dabbling duck, on the island of Kaua‘i, Hawai‘i, USA over 2013 and 2014. Additionally, we used contemporaneous Hawaiian Duck carcass recovery and surveillance data to examine temporal and climatic associations with avian botulism outbreaks. Our results suggested bi-monthly survival decreased with total rainfall during the preceding 2-month interval. Survival did not vary with sex, between peak and off-peak nesting seasons, or between the two years of this study. Annual survival probabilities (62–80%) were relatively low compared to the closely related Laysan Duck (Anas laysanensis) on Laysan Island. Primary causes of mortality included avian botulism and presumed predation by cats (Felis catus). The botulism surveillance dataset revealed support for the effect of rainfall on the number of sick and dead birds recovered (n = 216), with generally a greater number of recoveries during months with middle-range total rainfall during the concurrent and preceding months. Our study provides critical baseline demographic data for population monitoring and highlights the importance of managing botulism risk and non-native mammalian predators for the recovery of the endangered Hawaiian Duck.

Lessons from the Tōhoku tsunami: A model for island avifauna conservation prioritization.

Earthquake‐generated tsunamis threaten coastal areas and low‐lying islands with sudden flooding. Although human hazards and infrastructure damage have been well documented for tsunamis in recent decades, the effects on wildlife communities rarely have been quantified. We describe a tsunami that hit the world's largest remaining tropical seabird rookery and estimate the effects of sudden flooding on 23 bird species nesting on Pacific islands more than 3,800 km from the epicenter. We used global positioning systems, tide gauge data, and satellite imagery to quantify characteristics of the Tōhoku earthquake‐generated tsunami (11 March 2011) and its inundation extent across four Hawaiian Islands. We estimated short‐term effects of sudden flooding to bird communities using spatially explicit data from Midway Atoll and Laysan Island, Hawai'i. We describe variation in species vulnerability based on breeding phenology, nesting habitat, and life history traits. The tsunami inundated 21%–100% of each island's area at Midway Atoll and Laysan Island. Procellariformes (albatrosses and petrels) chick and egg losses exceeded 258,500 at Midway Atoll while albatross chick losses at Laysan Island exceeded 21,400. The tsunami struck at night and during the peak of nesting for 14 colonial seabird species. Strongly philopatric Procellariformes were vulnerable to the tsunami. Nonmigratory, endemic, endangered Laysan Teal (Anas laysanensis) were sensitive to ecosystem effects such as habitat changes and carcass‐initiated epizootics of avian botulism, and its populations declined approximately 40% on both atolls post‐tsunami. Catastrophic flooding of Pacific islands occurs periodically not only from tsunamis, but also from storm surge and rainfall; with sea‐level rise, the frequency of sudden flooding events will likely increase. As invasive predators occupy habitat on higher elevation Hawaiian Islands and globally important avian populations are concentrated on low‐lying islands, additional conservation strategies may be warranted to increase resilience of island biodiversity encountering tsunamis and rising sea levels.

Genetic admixture supports an ancient hybrid origin of the endangered Hawaiian duck.

Speciation is regarded primarily as a bifurcation from an ancestral species into two distinct taxonomic units, but gene flow can create complex signals of phylogenetic relationships, especially among different loci. We evaluated several hypotheses that could account for phylogenetic discord between mitochondrial DNA (mtDNA) and nuclear DNA (nuDNA) within Hawaiian duck (Anas wyvilliana), including stochastic lineage sorting, mtDNA capture and widespread genomic introgression. Our results best support the hypothesis that the contemporary Hawaiian duck is descended from an ancient hybridization event between the mallard (Anas platyrhynchos) and Laysan duck (Anas laysanensis). Whereas mtDNA clearly shows a sister relationship between Hawaiian duck and mallard, nuDNA is consistent with a genetic mosaic with nearly equal contributions from Laysan duck and mallard. In addition, coalescent analyses suggest that gene flow from either mallard or Laysan duck, depending on the predefined tree topology, is necessary to explain contemporary genetic diversity in Hawaiian ducks, and these estimates are more consistent with ancient, rather than contemporary, hybridization. Time since divergence estimates suggest that the genetic admixture event occurred around the Pleistocene-Holocene boundary, which is further supported by circumstantial evidence from the Hawaiian subfossil record. Although the extent of reproductive isolation from either putative parental taxon is not currently known, these species are phenotypically, genetically and ecologically different, and they meet primary criteria used in avian taxonomy for species designation. Thus, the available data are consistent with an admixed origin and support the hypothesis that the Hawaiian duck may represent a young hybrid species.

Microsatellite variation and rare alleles in a bottlenecked Hawaiian Islands endemic: implications for reintroductions

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 28:117-122 (2015) - DOI: https://doi.org/10.3354/esr00681 NOTE Microsatellite variation and rare alleles in a bottlenecked Hawaiian Islands endemic: implications for reintroductions Michelle H. Reynolds1,*, John M. Pearce2, Philip Lavretsky3, Pedro P. Seixas4, Karen N. Courtot1 1US Geological Survey, Pacific Island Ecosystems Research Center, PO Box 44, Hawai‘i National Park, Hawai‘i 96718, USA 2US Geological Survey, Alaska Science Center, 4210 University Drive, Anchorage, Alaska 99508, USA 3Wright State University, 3640 Colonel Glenn Hwy, Dayton, Ohio 45435, USA 4Centro de Reprodução Anatideos, Rua Mário Pais da Costa, no. 53, 3515-174 Viseu, Portugal *Corresponding author: mreynolds@usgs.gov ABSTRACT: Conservation of genetic biodiversity in endangered wildlife populations is an important challenge to address since the loss of alleles and genetic drift may influence future adaptability. Reintroduction aims to re-establish species to restored or protected ecosystems; however, moving a subset of individuals may result in loss of gene variants during the management-induced bottleneck (i.e. translocation). The endangered Laysan teal Anas laysanensis was once widespread across the Hawaiian archipelago, but became isolated on Laysan Island (415 ha) from the mid-1800s until 2004 when a translocation to Midway Atoll (596 ha) was undertaken to reduce extinction risks. We compared genetic diversity and quantified variation at microsatellite loci sampled from 230 individuals from the wild populations at Laysan (1999 to 2009) and Midway (2007 to 2010; n = 133 Laysan, n = 96 Midway birds). We identified polymorphic markers by screening nuclear microsatellites (N = 83). Low nuclear variation was detected, consistent with the species’ insular isolation and historical bottleneck. Six of 83 microsatellites were polymorphic. We found limited but similar estimates of allelic richness (2.58 alleles per locus) and heterozygosity within populations. However, 2 rare alleles found in the Laysan source population were not present in Midway’s reintroduced population, and a unique allele was discovered in an individual on Midway. Differentiation between island populations was low (FST = 0.6%), but statistically significant. Our results indicate that genetic drift had little effect on offspring generations 3 to 6 yr post-release and demonstrate the utility of using known founder events to help quantify genetic capture during translocations and to inform management decisions. KEY WORDS: Anas laysanensis · Island endemic · Genetic diversity · Laysan duck · Reintroduction biology Full text in pdf format PreviousNextCite this article as: Reynolds MH, Pearce JM, Lavretsky P, Seixas PP, Courtot KN (2015) Microsatellite variation and rare alleles in a bottlenecked Hawaiian Islands endemic: implications for reintroductions. Endang Species Res 28:117-122. https://doi.org/10.3354/esr00681 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 28, No. 2. Online publication date: July 14, 2015 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2015 Inter-Research.

Long-Term Monitoring of Endangered Laysan Ducks: Index Validation and Population Estimates 1998–2012

Abstract Monitoring endangered wildlife is essential to assessing management or recovery objectives and learning about population status. We tested assumptions of a population index for endangered Laysan duck (or teal; Anas laysanensis) monitored using mark–resight methods on Laysan Island, Hawai'i. We marked 723 Laysan ducks between 1998 and 2009 and identified seasonal surveys through 2012 that met accuracy and precision criteria for estimating population abundance. Our results provide a 15-y time series of seasonal population estimates at Laysan Island. We found differences in detection among seasons and how observed counts related to population estimates. The highest counts and the strongest relationship between count and population estimates occurred in autumn (September–November). The best autumn surveys yielded population abundance estimates that ranged from 674 (95% CI = 619–730) in 2003 to 339 (95% CI = 265–413) in 2012. A population decline of 42% was observed between 2010 and 2012 after consecutive storms and Japan's Tōhoku earthquake-generated tsunami in 2011. Our results show positive correlations between the seasonal maximum counts and population estimates from the same date, and support the use of standardized bimonthly counts of unmarked birds as a valid index to monitor trends among years within a season at Laysan Island.

Major histocompatibility I gene diversity in the critically endangered Laysan duck (Anas laysanensis).

Quantifying the genetic composition of founder populations is important to the success of reintroduction programmes, especially for bottlenecked and/or specialized species, such as island endemics. By implementing admixture schemes based on genetic variability, captive breeding programmes can minimize the detrimental effects of bottlenecking, inbreeding depression, outbreeding depression, etc. Particular attention has been given to genes within the major histocompatibility complex (MHC) due to their direct correlation to an individual’s immunity. However, isolating and amplifying MHC haplotypes remains difficult owing to the high diversity and paralogous nature. We describe a method of MHC I haplotype isolation based on an iterative process of primer design for the endangered island endemic, the Laysan duck (Anas laysanensis). Ultimately, haplotype-specific primers allow for direct genotyping after gel electrophoresis based on the presence/absence of their respective amplicons. Using the developed techniques, a total of eight unique haplotypes were isolated and assayed across 21 Laysan duck individuals from Laysan Island (N = 10) and Midway Atoll (N = 11). The presence/absence of seven haplotypes were variable across individuals with three haplotypes present in 95% of individuals, three in 38% of individuals, and one in 90% of individuals. The protocols described herein provide a simple, cost-effective method for isolating haplotypes and monitoring existing MHC variation in Laysan ducks, and the general approach can be applied to other molecular markers and species with low genetic diversity.

Demographic variation, reintroduction, and persistence of an island duck (Anas laysanensis )

Population variation in life history can be important for predicting successful establishment and persistence of reintroduced populations of endangered species. The Laysan duck (Anas laysanensis) is an endangered bird native to the Hawaiian Archipelago that was extirpated from most islands after the introduction of mammalian predators. Laysan ducks were restricted to a single remote island, Laysan Island (4.1 km2), for nearly 150 years. Since the species is not known to disperse between distant Hawaiian Islands today, 42 wild birds from Laysan Island were translocated to another mammalian predator-free low-lying atoll (Midway Atoll; 6.0 km2) to reduce extinction risk. We explored how variation in demography influences establishment and longer-term retention of genetic diversity (rare alleles) for reintroductions of this species. We observed dramatic differences in population growth between the source (λ = 1.18) and reintroduced (λ = 3.28) population. The number of eggs hatched at Midway Atoll was greater than at Laysan Island, however, we found no difference in hatching success (proportion of clutch hatched) between populations. Adult females produced 3 times as many fledglings per breeding year on Midway Atoll compared to Laysan Island. We estimated population abundance of both populations until 2010 and applied a Gompertz model with a Bayesian approach to infer density dependence, process variation, observation error, and carrying capacity for the Laysan Island and Midway Atoll populations. The carrying capacity from the Gompertz model for Midway Atoll (K = 883 ± 210 SD) was estimated to be greater than that of Laysan Island (K = 598 ± 76 SD). Translocations with small numbers of founders and no immigration can create population bottlenecks, leading to loss of genetic variation over time, and potentially reducing the reintroduced population's viability or its potential to serve as a source for future translocations. Therefore, we also assessed the probability of retaining rare alleles in an isolated reintroduced Laysan duck population using life history parameters observed from the Laysan Island and Midway Atoll populations; we concluded that additional founders are needed under scenarios using demographic estimates from both Laysan Island and Midway Atoll to retain either 90% or 95% of source population genetic diversity. © 2013 The Wildlife Society.

Experimental reintroduction reveals novel life-history variation in Laysan Ducks (Anas laysanensis)

ABSTRACT. Subfossil remains indicate that the Laysan Duck (Anas laysanensis) formerly occurred throughout the Hawaiian archipelago, but for more than 150 years it has been confined to a single, small atoll in the northwestern chain, Laysan Island. In 2004–2005, 42 ducks were reintroduced from Laysan to Midway Atoll, where they exhibited variation in life history never observed on Laysan. On Laysan, females have never been observed to breed successfully at age 1 year and few attempt it, whereas on Midway, females routinely raised young at <1 year of age. Mean (± SD) clutch size on Midway (7.0 ± 1.1, n = 41) was larger than the maximum clutch size of six eggs observed on Laysan. On Midway, renesting following nest failure (0.55 probability, n = 27) and double brooding (0.50, n = 54) were routine, and two instances of triple brooding were observed, whereas on Laysan, renesting and double brooding are rare (0.05 probability for both during our study; n = 21 and 19, respectively) and triple brooding has never ...

Influence of space use on fitness and the reintroduction success of the Laysan teal

AbstractTranslocation is an important tool for wildlife conservation and biodiversity restoration, but an inefficient one because of the unpredictability of success. Predictors of success such as habitat quality of the release site and number of individuals released have been identified, but the dynamics of successful translocations remain poorly understood. In particular, little is known about the relationship of individual post‐release movements to population establishment. In 2004, Laysan teal Anas laysanensis were reintroduced by translocating 20 wild birds from Laysan Island to Midway Atoll. Twenty‐two additional wild founders were brought the next year. We monitored the survival, reproductive success and movements of the 42 translocated individuals and their offspring for 4 years. Additionally, we monitored population size from 2004 to 2010. Unlike most translocations, we did not observe elevated post‐release mortality despite flight‐feather trimming to prevent immediate dispersal off‐island: first year survival was &gt; 90% and survival rates until 2009 were 0.65 ± 0.08 for founding adults. Laysan teal flew between the two main islands of Midway Atoll, and offspring had significantly larger maximum movement distances than founders. We monitored 84 nests and observed a significant, negative relationship of home range size to productivity for founding females. Flightless founders did not show fidelity to their release sites, but had strong fidelity to annual home ranges after attaining flight. Although we observed a component Allee effect on mate‐finding, this did not translate into a demographic Allee effect, and generally, the high fitness of founders contributed substantially to successful population establishment. Laysan teal abundance increased linearly until 2009, but showed evidence of population regulation afterwards. The population estimate was 473 (95% confidence interval 439–508) in 2010. On the much larger main Hawaiian Islands, we expect greater post‐release movement, a stronger component Allee effect, lower survival and lower reproductive rates because of predation to preclude successful reintroductions of this species to sites without predator management.

Postcatastrophe Population Dynamics and Density Dependence of an Endemic Island Duck

ABSTRACT Laysan ducks (Anas laysanensis) are restricted to approximately 9 km2 in the Northwestern Hawaiian Islands, USA. To evaluate the importance of density dependence for Laysan ducks, we conducted a Bayesian analysis to estimate the parameters of a Gompertz model and the magnitude of process variation and observation error based on the fluctuations in Laysan duck abundance on Laysan Island from 1994 to 2007. This model described a stationary distribution for the population at carrying capacity that fluctuates around a long‐term mean of 456 ducks and is between 316 to 636 ducks 95% of the time. This range of expected variability can be used to identify changes in population size that warn of catastrophic events. Density‐dependent population dynamics may explain the recovery of Laysan duck from catastrophic declines and allow managers to identify population monitoring thresholds.

Long-term Pair Bonds in the Laysan Duck

Abstract We describe long-term pair bonds in the endangered Laysan Duck (Anas laysanensis), a dabbling duck endemic to the Hawaiian Archipelago. Individually marked birds were identified on Laysan Island between 1998 and 2006 (n = 613 marked adults). We recorded pair bonds while observing marked birds, and documented within and between year mate switches and multi-year pair bonds. Twenty pairs banded before 2001 had stable pair bonds lasting ≥5 years with a maximum enduring pair bond of nine breeding seasons. Understanding reproductive strategy, including mate retention, would aid conservation planning and management efforts for the Laysan Duck. Further study is needed to characterize the social system of this endangered species.

Translocation and early post‐release demography of endangered Laysan teal

AbstractIn an attempt to reduce the high extinction risk inherent to small island populations, we translocated wild Laysan teal Anas laysanensis to a portion of its presumed prehistoric range. Most avian translocations lack the strategic post‐release monitoring needed to assess early population establishment or failure. Therefore, we monitored the survival and reproduction of all founders, and their first‐generation offspring using radio telemetry for 2 years after the first release. Forty‐two Laysan teal were sourced directly from the only extant population on Laysan Island and transported 2 days by ship to Midway Atoll. All birds survived the translocation with nutritional and veterinary support, and spent between 4 and 14 days in captivity. Post‐release survival of 42 founders was 0.857 (95% CI 0.86–0.99) during 2004–2006 or annualized 0.92 (95% CI 0.83–0.98). Seventeen of 18 founding hens attempted nesting in the first two breeding seasons. Fledgling success was 0.57 (95% CI 0.55–0.60) in 2005 and 0.63 (95% CI 0.62–0.64) in 2006. The effective founding female population (Ne) was 13. We applied these initial demographic rates to model population growth. The nascent population size increased to &gt;100 after only 2 years post‐release (λ=1.73). If this growth rate continues, the size of the Midway population could surpass the source population before 2010.

Postfledging Survival of Laysan Ducks

ABSTRACT Precise and unbiased estimates of demographic parameters are necessary for effective population monitoring and to parameterize population models (e.g., population viability analyses). This is especially important for endangered species, where recovery planning and managers' decisions can influence species persistence. In this study, we used mark—recapture methods to estimate survival of fledged juveniles (hatch‐yr [HY]) and adult (after‐hatch‐yr [AHY]) Laysan ducks (Anas laysanensis), an endangered anatid restricted to Laysan Island in the northwestern Hawaiian Islands. To better understand population dynamics, we examined how survival varied as a function of Laysan duck density during 1998–2004. Using random effects models, we also quantified process variation in survival, thereby quantifying the appropriate source of variation for future population models. The dataset supported variation in survival that was time (yr), age (AHY vs. HY), and sex specific. Due to small sample sizes, we did not examine time specificity in the survival of HY ducks. Survival of HY ducks was 0.832 (SE = 0.087) for females (n = 21) and 0.999 (SE &lt; 0.001) for males (n = 15) during 1998–2001. Trends in time and density lacked support as sources of variation in the survival of AHY ducks during 1998–2004. After‐hatch‐year survival ranged from 0.792 (SE = 0.033) to 0.999 (SE &lt; 0.001). Where we modeled survival as a random effect, annual survival for AHY females was 0.881 (SE = 0.017) and process variation (σs) was 0.034. For AHY males, annual survival (μs) was 0.906 (SE = 0.019) and process variation (σs) was 0.040. This information will improve existing population viability analysis models for Laysan ducks. We believe that monitoring the source and translocation populations will be paramount for increasing our understanding of Laysan duck dynamics, recovery planning, and population management.

Mortality in Laysan ducks (Anas laysanensis) by emaciation complicated by Echinuria uncinata on Laysan Island, Hawaii, 1993.

In November 1993, unusual mortality occurred among endangered Laysan ducks on Laysan Island, one of the remote refugia of the Northwestern Hawaiian Islands National Wildlife Refuge (USA). Ten live ducks were emaciated, and blood samples documented anemia, heterophilia, and eosinophilia. Pathology in 13 duck carcasses revealed emaciation, marked thickening of the proventricular wall, abundant mucus, and nodules in the gastrointestinal tract. Histology revealed granulomata associated with nematodes in the proventriculus, small intestines, and body walls of nine of 10 ducks examined on histology. We suspect that low rainfall and low food abundance that year contributed to enhanced pathogenicity of parasite infection, either through increased exposure or decreased host resistance. Because the Laysan duck is found only on Laysan island and is critically endangered, translocation of this species to other islands is being considered. Given that we have not seen pathology associated with Echinuria spp. in native waterfowl on other Hawaiian Islands and given the parasite's potential to cause significant lesions in Laysan ducks, it will be important to prevent the translocation of Echinuria spp.

Habitat Use and Home Range of the Laysan Teal on Laysan Island, Hawaii

Abstract The 24-hour habitat use and home range of the Laysan Teal (Anas laysanensis), an endemic dabbling duck in Hawaii, was studied using radio telemetry during 1998-2000. Radios were retained for a mean of 40 days (0-123 d; 73 adult birds radio-tagged). Comparisons of daily habitat use were made for birds in the morning, day, evening, and night. Most birds showed strong evidence of selective habitat use. Adults preferred the terrestrial vegetation (88%), and avoided the lake and wetlands during the day. At night, 63% of the birds selected the lake and wetlands. Nocturnal habitat use differed significantly between the non-breeding and breeding seasons, while the lake and wetland habitats were used more frequently during the non-breeding season. Most individuals showed strong site fidelity during the study, but habitat selection varied between individuals. Mean home range size was 9.78 ha (SE ± 2.6) using the fixed kernel estimator (95% kernel; 15 birds, each with >25 locations). The average minimum con...

Censusing Laysan Ducks Anas laysanensis: a lesson in the pitfalls of estimating threatened species populations

SummaryThe Laysan Duck Anas laysanensis is a threatened species endemic to Laysan Island, Hawaü U.S.A., with a population that appears subject to severe fluctuation, although this may be attributable to different census methods. The most effective method used so far has been one that notes the ratio of marked to unmarked birds seen on censuses conducted at dusk around the central lake. In 1986 and 1987, weekly censuses were made from which population estimates were derived with the Lincoln—Petersen Index: the current population is approximately 500. The ducks were least visible during the nesting and moulting periods of spring and summer, and population estimates were significantly lower during that period in both 1986 and 1987. This phenomenon calls in doubt other estimates and probably accounts for the fluctuations noted in previous years. Thus careful attention should be given to potential problems in monitoring threatened species populations, because without a clear understanding of the ecology of the threatened species, population estimates could suggest inappropriate management measures.

20. On the ecology of hypersaline lagoons on Laysan Atoll and Kauai Island, Hawaii, with special reference to the Laysan duck, Anas laysanensis Rothschild

20. On the ecology of hypersaline lagoons on Laysan Atoll and Kauai Island, Hawaii, with special reference to the Laysan duck, Anas laysanensis Rothschild