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 < 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 < 0.001). Where we modeled survival as a random effect, annual survival for AHY females was 0.881 (SE = 0.017) and process variation (σ_s) was 0.034. For AHY males, annual survival (μ_s) was 0.906 (SE = 0.019) and process variation (σ_s) 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.     

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.     

A geological perspective of the upland biota of Laysan atoll (Hawaiian Islands)

Laysan Island, a low atoll in the Leeward Hawaiian Islands, exhibits a biota that contains nine genera of upland and montane lineages of animals and plants usually of restricted range and occurrence and adapted to high island habitats. The geological history of Laysan Island, interpreted in terms of plate tectonic theory and recent ideas on the formation of linear island chains, shows that Laysan existed as an active high volcanic island approximately 15 million years ago. Since that time subaerial erosion and tectonic subsidence have combined to reduce the height of the island. During the past 250,000 years glacioeustatic sea level changes have resulted in Laysan Island fluctuating, geomorphologically, between a high limestone island and an atoll status. Laysan is viewed as a refugium for upland and montane lineages able to keep pace, via great adaptive flexibility, with drastic habitat changes. The thesis that plants of Laysan are recent arrivals is considered unlikely, as regards the upland contingent, in view of the geological history of the island.     

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.     

Demography of Bristle-thighed Curlews Numenius tahitiensis wintering on Laysan Island

We studied the nonbreeding ecology of Bristle-thighed Curlews Numenius tahitiensis from 1988 to 1991 on Laysan Island in the Northwestern Hawaiian Islands. Using capture-recapture analysis, we estimated that 300–350 curlews wintered on the island. Annual survival was >85% for adults and 92% for first-year birds. Young birds remained on the island until at least their third calendar year, when some individuals made "exploratory" visits to other islands in the Northwestern chain. Most of the birds marked in their first year migrated north to the breeding grounds when they were 3 years old; several birds remained on the island until they were at least 4 years old. Adults returned to the same discrete home ranges year after year, whereas subadults (which do not migrate) tended to use a greater portion of the island. At least 60% of the subadults marked from 1988 to 1990 returned to the island to winter as adults. Because young curlews arrived after adults and experienced high survivorship while on the island, there did not appear to be intense competition for space at Laysan even though the island is at the northern end of the species' winter range.     

Distribution and frequencies of shark-inflicted injuries to the endangered Hawaiian monk seal (Monachus schauinslandi)

I analyzed the frequencies of wounds inflicted by sharks to the endangered Hawaiian monk seal Monachus schauinslandi at three colonies in the Northwestern Hawaiian Islands between 1990 and 2000. I applied specific criteria typical of shark bites to all injuries to avoid bias. Pooling data from all years and the three colonies revealed several patterns. Sharks injured more pups (nursing and weaned) and juveniles (1–2 years old) than adults and subadults. More female pups and male juveniles than any other size classes were injured by sharks. Almost all (97%) of the injured pups were from French Frigate Shoals. More juveniles than expected were wounded at Laysan Island and Lisianski Island. Most shark wounds were between the diaphragm and the pelvic girdle, but pups were bitten most often just behind the pelvis compared with adults who were bitten more often near the head and neck.     

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.     

Early development and differentiation of the Laysan albatross (Phoebastria immutabilis (Rothschild, 1893): Procellariiformes)

Bird incubation is subdivided into two phases: differentiation (embryonic phase) and growth (fetal phase). Most birds have a relatively short incubation period (20–30 days) with the phase transition occurring midway through the incubation period. The Laysan albatross (Phoebastris immutabilis) is a large pelagic bird with a long incubation period. The purpose of this study was to document the differentiation phase with the aim of ascertaining the impact of a lengthened incubation on embryonic development. Eighty‐two previously collected albatross embryos were examined, measured, and staged. The albatross was found to develop more slowly than smaller birds, with a rate similar to other long‐incubating birds. Legs and wings grow at similar rates but exhibit variation in growth among their anatomical components. While the albatross embryos shared some morphological stages with chickens, they were more similar to ducks and pelicans. Special features of the albatross not shared with the Gallianserae (chickens and ducks) included an alligator‐like curved tail, narial tubes, and a cloacal bulge. Further examination of other larger pelagic birds with long incubation periods are needed to determine the uniqueness of the Laysan albatross embryonic development. Although much embryonic phase growth was documented in the postnatal period, little is known about the later, fetal phase in Laysan albatross. Future studies should involve examination of later (post day 32) fetuses. J. Morphol. 277:1231–1249, 2016. © 2016 Wiley Periodicals, Inc.     

Phylogeography of the New Zealand blue duck (<Emphasis Type="Italic">Hymenolaimus malacorhynchos</Emphasis>): implications for translocation and species recovery

Translocation of individuals among extant populations is an important tool in species conservation that allows managers to supplement dwindling populations and potentially alleviate the deleterious effects of inbreeding. Ideal translocation strategy should consider historical relationships among existing populations to avoid potential disruption of population subdivision and local adaptation. Here, we examine mitochondrial sequence variation in the endangered blue duck Hymenolaimus malacorhynchos, a New Zealand endemic riverine specialist, to facilitate informed decision making in future translocations. Behavioural observations suggest that blue duck dispersal is limited and may result in genetic structure within and between regional populations. We analysed 894 base pairs of mitochondrial control region in 78 adult blue ducks sampled from 11 river catchments across the species’ range (representing four regions in the North Island and three regions in the South Island) and found strong and significant genetic structure both within and among islands. These results, combined with a 2.0% sequence divergence between islands, indicates that North Island and South Island blue ducks should be treated as separate management units. The relationship between genetic differentiation and geographic distance for blue ducks on the South Island conformed to an “isolation by distance” pattern. Overall, we recommend that translocations of blue ducks should not be made between the North and the South Islands and those within each island should be restricted to neighbouring catchments.     

Persistence of an endangered native duck,feral mallards,and multiple hybrid swarms across the main Hawaiian Islands

Interspecific hybridization is recognized as an important process in the evolutionary dynamics of both speciation and the reversal of speciation. However, our understanding of the spatial and temporal patterns of hybridization that erode versus promote species boundaries is incomplete. The endangered, endemic koloa maoli (or Hawaiian duck, Anas wyvilliana) is thought to be threatened with genetic extinction through ongoing hybridization with an introduced congener, the feral mallard (A. platyrhynchos). We investigated spatial and temporal variation in hybrid prevalence in populations throughout the main Hawaiian Islands, using genomic data to characterize population structure of koloa, quantify the extent of hybridization, and compare hybrid proportions over time. To accomplish this, we genotyped 3,308 double‐digest restriction‐site‐associated DNA (ddRAD) loci in 425 putative koloa, mallards, and hybrids from populations across the main Hawaiian Islands. We found that despite a population decline in the last century, koloa genetic diversity is high. There were few hybrids on the island of Kaua?i, home to the largest population of koloa. By contrast, we report that sampled populations outside of Kaua?i can now be characterized as hybrid swarms, in that all individuals sampled were of mixed koloa × mallard ancestry. Further, there is some evidence that these swarms are stable over time. These findings demonstrate spatial variation in the extent and consequences of interspecific hybridization, and highlight how islands or island‐like systems with small population sizes may be especially prone to genetic extinction when met with a congener that is not reproductively isolated.     

Microsatellite markers for two stifftail ducks: the white‐headed duck,Oxyura leucocephala,and the ruddy duck,O. jamaicensis

Hybridization with a close relative, the North American ruddy duck (Oxyura jamaicensis), is a major problem for the conservation of the endangered white‐headed duck (Oxyura leucocephala). We report the development of 11 microsatellite markers that can facilitate the identification of hybrids as well as the study of the population structure of both species across their distributions. These markers were tested in 63 white‐headed ducks and 50 ruddy ducks and show a larger diversity in the latter species.     

Hybridization between white-headed ducks and introduced ruddy ducks in Spain

The ruddy duck, Oxyura jamaicensis, was introduced to Great Britain in the mid-20th century and has recently spread to other Western European countries. In Spain, ruddy ducks hybridize with the globally endangered white-headed duck, Oxyura leucocephala. We assessed the effects of hybridization on the Spanish white-headed ducks, which constitute 25% of the global population of this species, using a panel of eight nuclear intron markers, 10 microsatellite loci, and mtDNA control region sequences. These data allowed parental individuals, F(1) hybrids, and the progeny of backcrossing to be reliably distinguished. We show that hybrids between the two species are fertile and produce viable offspring in backcrosses with both parental species. To date, however, we found no extensive introgression of ruddy duck genes into the Spanish white-headed duck population, probably due to the early implementation of an effective ruddy duck and hybrid control programme. We also show that genetic diversity in the expanding European ruddy duck population, which was founded by just seven individuals, exceeds that of the native Spanish white-headed duck population, which recently recovered from a severe bottleneck. Unless effective control of ruddy ducks is continued, genetic introgression will compromise the unique behavioural and ecological adaptations of white-headed ducks and consequently their survival as a genetically and evolutionary distinct species.     

Infectious disease monitoring of the endangered Hawaiian monk seal

As part of conservation efforts between 1997 and 2001, more than 25% (332 animals) of the endangered Hawaiian monk seal (Monachus schauinslandi) population was sampled in the northwestern Hawaiian Islands. Serum samples were tested for antibodies to viruses, bacteria, and parasites known to cause morbidity and mortality in other marine mammal species. Antibodies were found to phocine herpesvirus-1 by using an enzyme-linked immunosorbent assay, but seropositive results were not confirmed by virus neutralization test. Antibodies to Leptospira bratislava, L. hardjo, L. icterohaemorrhagiae, and L. pomona were detected in seals from several sites with the microagglutination test. Antibodies to Brucella spp. were detected using 10 conventional serologic tests, but because of inconsistencies in test results and laboratories used, and the lack of validation by culture, the Brucella serology should be interpreted with caution. Antibodies to B. canis were not detected by card test. Chlamydophila abortus antibodies were detected by complement fixation (CF) test, and prevalence increased significantly as a function of age; the low sensitivity and specificity associated with the CF make interpretation of results difficult. Antibodies to Toxoplasma gondii and Dirofilaria immitis were rarely found. There was no serologic evidence of exposure to four morbilliviruses, influenza A virus, canine adenovirus, caliciviruses, or other selected viruses. Continuous surveillance provides a means to detect the introduction or emergence of these or other infectious diseases, but it is dependent on the development or improvement of diagnostic tools. Continued and improved surveillance are both needed as part of future conservation efforts of Hawaiian monk seals.     

Production of chicken progeny (Gallus gallus domesticus) from interspecies germline chimeric duck (Anas domesticus) by primordial germ cell transfer

The present study aimed to investigate the differentiation of chicken (Gallus gallus domesticus) primordial germ cells (PGCs) in duck (Anas domesticus) gonads. Chimeric ducks were produced by transferring chicken PGCs into duck embryos. Transfer of 200 and 400 PGCs resulted in the detection of a total number of 63.0 ± 54.3 and 116.8 ± 47.1 chicken PGCs in the gonads of 7-day-old duck embryos, respectively. The chimeric rate of ducks prior to hatching was 52.9% and 90.9%, respectively. Chicken germ cells were assessed in the gonad of chimeric ducks with chicken-specific DNA probes. Chicken spermatogonia were detected in the seminiferous tubules of duck testis. Chicken oogonia, primitive and primary follicles, and chicken-derived oocytes were also found in the ovaries of chimeric ducks, indicating that chicken PGCs are able to migrate, proliferate, and differentiate in duck ovaries and participate in the progression of duck ovarian folliculogenesis. Chicken DNA was detected using PCR from the semen of chimeric ducks. A total number of 1057 chicken eggs were laid by Barred Rock hens after they were inseminated with chimeric duck semen, of which four chicken offspring hatched and one chicken embryo did not hatch. Female chimeric ducks were inseminated with chicken semen; however, no fertile eggs were obtained. In conclusion, these results demonstrated that chicken PGCs could interact with duck germinal epithelium and complete spermatogenesis and eventually give rise to functional sperm. The PGC-mediated germline chimera technology may provide a novel system for conserving endangered avian species.     

Incubation energetics of the Laysan Albatross

Summary The energy expenditure of incubating and foraging Laysan Albatross (Diomedea immutabilis, mean body weight 3.07 kg) was estimated by means of the doubly-labelled water technique. During incubation, the energy expenditure was similar to that of resting birds that were not incubating an egg. The energy expenditure of foraging albatross (2072 kJ/day) was 2.6 times that of resting birds. It was concluded that the energy expenditure of the tropical Laysan Albatross was not less than that of species foraging over cold, high-latitude oceans. An energy budget compiled for an incubating pair of albatross revealed that the energy expenditure of the female was greater than that of the male bird, during the incubation period.     

Translocation and early post-release demography of endangered Laysan teal

In 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 ( N _e) was 13. We applied these initial demographic rates to model population growth. The nascent population size increased to >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.     

Gastrointestinal helminths of the Mexican duck, Anas platyrhynchos diazi Ridgway, from north central Mexico and southwestern United States

Twenty-five species of helminths, recovered from the gastrointestinal tracts of 129 Mexican ducks from Mexico and the United States, were all new host records. The species included: Echinoparyphium recurvatum, Echinostoma revolutum, Hypoderaeum conoideum, Notocotylus attenuatus, Prosthogonimus cuneatus, Zygocotyle lunata, Anomotaenia ciliata, Cloacotaenia megalops, Diorchis bulbodes, Diorchis sp., Drepanidotaenia lanceolata, Echinocotyle rosseteri, Fimbriaria fasciolaris, Fimbriarioides sp., Hymenolepis sp. 1, Hymenolepis sp. 2, Sobolevicanthus gracilis. Corynosoma constrictum, Polymorphus minutus, Amidostomum acutum, Echinuria sp., Epomidiostomum crami, Hystrichis varispinosus, Rusguniella arctica, and Tetrameres sp. Fimbriarioides sp. occurred predominantly in ducks from south-central Chihuahua, Mexico. The distributions for the other 24 species of the helminths were not significantly different among the four collecting areas. The helminth fauna for the 32 complete specimens and 97 intestinal tracts was distributed relatively evenly among the hosts with a calculated mean evenness of 0.77 +/- 0.15 and 0.89 +/- 0.03 respectively. The parasite fauna was more similar to those of the black duck Anas rubripes Brewster of eastern North America (53%), the mallard, Anas platyrhynchos (L.) (49%), and the mottled duck, Anas fulvigula Ridgway, from Florida (45%), than to the green-winged teal, Anas crecca (L.) (36%), the gadwall, Anas strepera (L.) (30%), and the American wigeon, Anas americana Gmelin (26%), collected in the Southwest.     

Genetic studies facilitated management decisions on the invasion of the ruddy duck in Europe

The ruddy duck (Oxyura jamaicensis), a stifftail native to the Americas, was introduced to the UK in the 1950s and has since been recorded in 22 western Palearctic countries. By 2000, the UK population peaked at nearly 6,000 individuals. In 1991, hybridisation with the native and globally threatened (IUCN Endangered) white-headed duck (Oxyura leucocephala), a stifftail restricted to the Mediterranean and Asia, was recorded in Spain and culling of hybrids and ruddy ducks began. Here we report on a series of genetic studies that have enabled and supported management decisions to the benefit of the white-headed duck. First, genetic data confirmed that these are two distinct species, each of which is more closely related to other stifftail species. Second, molecular studies indicated that ruddy ducks in Spain, Iceland and elsewhere in Europe were of captive origin and not descendants from vagrants from their native North America. Third, genetic methods were used to distinguish among different hybrid generations in Spain and detected no ruddy duck introgression in birds identified morphologically as white-headed ducks. Collectively, these results supported management decisions to eradicate ruddy ducks from Europe. Subsequently, a control programme reduced the UK population by over 95 % by 2010, and the arrival of ruddy ducks to Spain decreased from 21 birds in 2003 to two sightings in 2010–2011. However, increased efforts to control small ruddy duck populations elsewhere in Europe and Morocco are still required to ensure conservation of the white-headed duck. This case of invasion by hybridization demonstrates that successful control is feasible given early detection followed by a rapid response plan; it also shows the contribution of research to management and that to guarantee the conservation of an endangered native species action may be required in countries outside its distribution range.     

Prevalence of avian pox virus and effect on the fledging success of Laysan Albatross

ABSTRACT.   Avian pox virus ( Poxvirus avium ) is a mosquito-borne disease that occurs worldwide in a variety of bird species, but little is known about its prevalence or effect on seabirds. We monitored prevalence of pox virus and its effect on fledging success of Laysan Albatross ( Phoebastria immutabilis ) on Oahu, Hawaii, from 2003 to 2007. Pox prevalence in albatross chicks averaged 88% in years with high rainfall and 3% in years with low rainfall. Diagnosis of pox virus was clinically confirmed in two birds by Muscovy Duck ( Cairina moschata ) fibrolast cultures. Severity of infection ranged from small wart-like nodules and lesions on the bill, face, eyes, tarsus, and feet, to large tumorous growths that completely covered both eyes and caused deformation of the bill and skull. Most chicks recovered from infection, and the fledging rate in pox epizootic years (82%) did not differ from that in years with low pox prevalence (80%) or the average fledging rate on Midway Atoll (86%). Three chicks with severe infections were resighted as healthy adults on Kauai and Oahu in 2007, confirming postfledging survival of at least some birds. The high recovery rate, fledging success, and postfledging survival indicate that Laysan Albatross have strong immunity to avian pox virus.     

Cutaneous herpesvirus infection in a mallard duck (Anas platyrhynchos)

Investigations of mortalities involving wild mallard ducks (Anas platyrhynchos) revealed the presence of a herpesvirus associated with skin lesions on the plantar surface of the foot web of one duck. Ultrastructurally, the paracrystalline arrays of viral core particles and unencapsidated nucleoids in the nucleus, and the enveloped viruses in cytoplasmic vacuoles are compatible with a herpesvirus. This appears to be the first report of cutaneous lesions in a mallard duck attributable to a herpesvirus. Whether this lesion is due to duck virus enteritis (DVE), suggesting that cutaneous shedding is possible, or due to another uncharacterized herpesvirus of ducks is unclear.