79 research outputs found
Ecology of the Black-faced sheathbill on Marion Island
Thesis (PhD)--Stellenbosch University, 2013.ENGLISH ABSTRACT: As the pace of climate change has begun to accelerate so too has it become clear that the
direct impacts thereof are likely to have profound consequences for many island systems.
Moreover, it has also been suggested that climate change will exacerbate the effects of
many invasive species, so further impacting both diversity and ecosystem functioning.
Forecasts for such interactions have been most pronounced for the Southern Ocean islands,
which are home to a wide variety of endemic species. This thesis is about such interactions
and their specific impacts on a key endemic, the black-faced sheathbill (Chionis minor) on
the Prince Edward Islands.
Of increasing concern is how invasive rodent populations in the Southern Ocean may
be responding to global climate change, as ameliorating conditions on these islands are
forecast to decrease thermal and resource restrictions on rodents. However, firm evidence
for changing rodent populations in response to climate change, and demonstrations of
associated impacts on the terrestrial environment, are entirely absent for the region. In
Chapter 2 of this thesis, these relationships are explored for invasive house mice (Mus
musculus) on Marion Island. Using spatially explicit capture-recapture modeling, it is
determined that mouse populations across a range of habitats have increased over time.
Owing to an extended breeding season, made possible by ameliorating conditions brought
on by climate change, the total number of mice on the island at annual peak density more
than doubled over the past decade. It is also demonstrated that mice directly reduce
invertebrate densities, with biomass losses up to two orders of magnitude in some habitats.
Because of the importance of invertebrates to nutrient cycling on the island, such changes
are likely to have significant ecosystem-level impacts.
In Chapter 3 the focus expands to examine how increasing mouse impacts and other
outcomes of climate change are affecting the ecology of the black-faced sheathbill. It has
been established that invasive house mice are capable of suppressing the populations of
several seabird species in the Southern Ocean. However, mouse impacts on the region’s few
island endemic land-birds remain largely unexplored. Further, a significant effect of climate
change may be realized by altering interspecific interactions, specifically food webs. A
significant portion of sheathbill diets is derived from rockhopper penguins, a species
currently under a climate-change-driven decline, which may have significant effects on
sheathbills. The study found that terrestrial invertebrates are no longer a significant prey resource for sheathbills on Marion Island, and that sheathbills have effectively been
displaced from a formerly important winter food resource by mice. In response, the number
of sheathbills foraging in king penguin colonies increased. Moreover, a reduced rockhopper
penguin population lead to significant declines in both the number and proportion of
sheathbills foraging in rockhopper penguin colonies. The sum result was a significant decline
in the body condition of female sheathbills. Rather than decrease reproductive output,
sheathbills responded by decreasing clutch size and producing significantly fewer male
nestlings. While population estimates did not detect a reduction in the number of
sheathbills, population projections suggest that the population is in decline, with the
reproductive population declining faster than the absolute population.
There is need for greater study of island species, as for even relatively well-studied
taxa such as birds many aspects of ecology remain significantly less studied when compared
to species occurring on continents. For example, basal metabolic rate (BMR) is a
fundamental characteristic of all endotherms, yet only a handful of island birds have had
their BMR measured, and fewer still to a level that allows intraspecific analysis. In Chapter 4
the BMR of black-faced sheathbills on Marion Island was measured to determine whether
the unique phylogenetic position and ecology of sheathbills equate to a unique BMR when
allometrically compared to other birds. It was found that the BMR of sheathbills is typical for
a bird of its size. However, significant intraspecific variation was found to occur, with
differences in habitat quality a likely driver.
The results of the study show that the combined effects of climate change and
invasive species can have significant consequences for terrestrial endemics in the Southern
Ocean. Further, the long-term changes observed in sheathbills make clear the need for
improved documentation and study of island species in general, as many of the responses
observed in this study are significant but subtle and would not have been evident without
detailed knowledge of species ecology and vital rates. Giving greater focus to insular biota is
imperative to understanding their current status and ecology as well as establishing a
barometer against which further global change can be measured and mitigation measures
evaluated. Specific conservation responses for the black-faced sheathbill on Marion Island
include the provision of nest boxes at king penguin colonies, and eradication of house mice. The latter would have long-term benefits for the species, invertebrates, ecosystem
functioning generally, and likely also for important seabirds such as several species of
albatrosses whose chicks are being increasingly preyed on by mice. Eradication would,
however, be difficult and expensive, and with substantial potential non-target effects,
including on sheathbills, that would have to be carefully managed. In the absence of local
mouse eradication, and with ongoing climate change, specific management of the sheathbill
population through the provision of supplementary nesting sites seems the most
appropriate conservation action. It should therefore be examined in small-scale trials to
ascertain the likelihood of unintended consequences. Importantly, the maintenance of
Prince Edward Island as largely free of invasive species is key to the conservation of the local
black-faced sheathbill subspecies, Chionis minor marionensis, endemic to the Prince Edward
Island group.AFRIKAANSE OPSOMMING: Soos die tempo van klimaatsverandering begin om te versnel, het dit ook duidelik geword
dat die direkte impak daarvan waarskynlik ernstige gevolge vir baie eilande gaan hê. Verder
word dit is ook voorgestel dat klimaatsverandering die gevolge van baie indringerspesies sal
vererger, so ʼn verdere impak het op beide diversiteit en die funksionering van die
ekosisteem. Voorspellings vir sulke interaksies is die meeste uitgespreek vir die Suidelike
Oseaan-eilande, wat ook die tuiste van 'n wye verskeidenheid van endemiese spesies is.
Hierdie tesis is oor sulke interaksies en hul spesifieke impak op 'n sleutel endemiese spesie
is, die swart gesig skedebek (Chionis minor) op die Prince Edward-eilande.
ʼn Groter bron van bekommernis is hoe uitheemse knaagdier bevolkings in die
Suidelike Oseaan kan reageer teenoor globale klimaatsverandering, aangesien toestande op
die eilande voorspel word om hitte en hulpbron beperkings vir knaagdiere te verminder.
Maar, ferm bewyse vir die verandering van knaagdier bevolkings in reaksie op
klimaatsverandering, en demonstrasies van gepaardgaande impakte op die terrestriële
omgewing, is heeltemal afwesig vir die streek. In Hoofstuk 2 van hierdie tesis, word hierdie
verhoudings ondersoek vir indringende huis muise (Mus musculus) op Marion-eiland.
Ruimtelik vang-terugvang modelle word gebruik om vas te stel dat die muis bevolkings oor 'n
verskeidenheid van habitatte mettertyd toegeneem het. As gevolg van 'n uitgebreide
broeiseisoen as gevolg van die verligting van toestande gebring deur klimaatsverandering,
het die totale aantal muise op die eiland by die jaarlikse hoogtepunt digtheid meer as
verdubbel oor die afgelope dekade. Dit is ook getoon dat muise die digtheid van
ongewerweldes direk verminder het, met biomassa verliese tot twee ordes in sommige
habitatte. As gevolg van die belangrikheid van die ongewerweldes vir voedingstof sirkulering
op die eiland, behoort sulke veranderinge waarskynlik 'n beduidende ekosisteem-vlak impak
te hê.
In Hoofstuk 3 word die fokus verbreed om te sien hoe die verhoging van die muis
impakte en ander uitkomste van klimaatsverandering die ekologie van die swart gesig
skedebek beïnvloed. Daar is vasgestel dat indringende huis muise in staat is om die
bevolkings van verskeie spesies seevoëls te onderdruk in die Suidelike Oseaan. Maar die
muis impak op die streek se paar eiland endemiese land voëls bly grootliks onverken. Verder
kan 'n beduidende uitwerking van klimaatsverandering verwesenlik word deur die wysiging van interspesifieke interaksies, veral voedselwebbe. 'n Beduidende gedeelte van skedebek
dieet word gekry van Geelkuifpikkewyne, 'n spesie wat tans onder 'n klimaat-veranderinggedrewe
agteruitgang is, wat ook 'n beduidende uitwerking het op die skedebek. Die studie
het gevind dat terrestriële ongewerweldes nie meer 'n beduidende prooi hulpbron vir die
skedebek op Marion-eiland is nie, en dat die skedebek effektief is verplaas uit 'n voorheen
belangrike winter kos hulpbron deur muise. In reaksie hierop het die aantal skedebekke wat
kos soek in die koning pikkewyn kolonies toegeneem. Verder, 'n verlaagde Geelkuifpikkewyn
bevolking lei tot 'n beduidende afname in beide die aantal en persentasie van skedebekke
wat kos soek in Geelkuifpikkewyn kolonies. Die gevolg was 'n beduidende afname in die
liggaamstoestand van die vroulike skedebekke. Eerder as ʼn afname van reproduksie, het
skedebekke gereageer deur 'n vermindering in die aantal eiers en produseer aansienlik
minder manlike kuikens. Terwyl bevolking skattings nie 'n afname in die aantal skedebekke
kan vind nie, dui bevolking projeksies daarop dat die bevolking besig is om af te neem, met
die voortplanting bevolking wat vinniger daal as die absolute bevolking.
Daar is 'n behoefte vir 'n groter studie van eiland spesies, omdat selfs vir betreklik
goed bestudeerde groepe soos voëls baie aspekte van die ekologie aansienlik minder
bestudeer bly in vergelyking met spesies op die vastelande. Byvoorbeeld, basale metaboliese
tempo (BMT) is 'n fundamentele kenmerk van alle endotermiese diere, maar net 'n
handjievol van die eiland voëls het hul BMT laat meet, en nog minder tot 'n vlak wat dit
moontlik maak intraspesifieke analise. In Hoofstuk 4 was die BMT van die swart gesig
skedebek op Marion-eiland gemeet om te bepaal of die unieke filogenetiese posisie en
ekologie van skedebekke gelyk aan 'n unieke BMT wanneer allometries vergelyk word met
ander voëls. Daar is gevind dat die BMT van skedebekke tipies is vir 'n voël van sy grootte.
Daar is egter belangrike intraspesifieke variasie gevind, met verskille in habitat kwaliteit as 'n
waarskynlike verduideliking. Die resultate van die studie toon dat die gekombineerde effek van
klimaatsverandering en indringerspesies beduidende gevolge vir terrestriele inheemse
spesies in die Suidelike Oseaan kan hê. Verder maak die lang-termyn veranderinge
waargeneem in skedebekke dit duidelik dat die behoefte aan verbeterde dokumentasie en
studie van die eiland spesies in die algemeen, omdat baie van die reaksies waargeneem in
hierdie studie betekenisvol is, maar subtiel en sou nie gewees het sonder gedetailleerde
kennis van die spesies ekologie van die spesie nie. Om ʼn groter fokus op die insulêre biota te plaas is noodsaaklik om hul huidige status en die ekologie te begryp, sowel as om 'n
barometer waarteen verdere globale verandering gemeet kan word en versagtende
maatreëls geëvalueer.
Spesifieke bewaring antwoorde vir die swart gesig skedebek op Marion-eiland sluit in
die voorsiening van nes bokse by koning pikkewyne, en die uitwissing van huis muise.
Laasgenoemde sou lang-termyn voordele vir die spesie en ongewerweldes hê, asook
funksionering van die ekosisteem in die algemeen, en waarskynlik ook vir belangrike
seevoëls soos verskeie spesies van albatrosse wie se kuikens toenemend geëet word deur
muise. Uitwissing sou egter moeilik en duur wees, en het 'n aansienlike potensiaal vir nieteiken
effekte, insluitend op skedebekke, wat sal versigtig moet bestuur word. In die
afwesigheid van plaaslike muis uitwissing, en met voortdurende verandering van die klimaat,
spesifieke bestuur van die skedebek bevolking deur die voorsiening van aanvullende
broeiplekke blyk die mees geskikte bewaringsaksie. Dit moet dus ondersoek word in 'n kleinskaal
proewe om die waarskynlikheid van onbedoelde gevolge te bepaal. Wat belangrik is
die instandhouding van Prince Edward Eiland as grootliks vry van indringerspesies en is die
sleutel tot die bewaring van die plaaslike swart gesig skedebek subspesie, Chionis minor
marionensis, endemies aan die Prince Edward Eiland groep
Upper limits on the strength of periodic gravitational waves from PSR J1939+2134
The first science run of the LIGO and GEO gravitational wave detectors
presented the opportunity to test methods of searching for gravitational waves
from known pulsars. Here we present new direct upper limits on the strength of
waves from the pulsar PSR J1939+2134 using two independent analysis methods,
one in the frequency domain using frequentist statistics and one in the time
domain using Bayesian inference. Both methods show that the strain amplitude at
Earth from this pulsar is less than a few times .Comment: 7 pages, 1 figure, to appear in the Proceedings of the 5th Edoardo
Amaldi Conference on Gravitational Waves, Tirrenia, Pisa, Italy, 6-11 July
200
Improving the sensitivity to gravitational-wave sources by modifying the input-output optics of advanced interferometers
We study frequency dependent (FD) input-output schemes for signal-recycling
interferometers, the baseline design of Advanced LIGO and the current
configuration of GEO 600. Complementary to a recent proposal by Harms et al. to
use FD input squeezing and ordinary homodyne detection, we explore a scheme
which uses ordinary squeezed vacuum, but FD readout. Both schemes, which are
sub-optimal among all possible input-output schemes, provide a global noise
suppression by the power squeeze factor, while being realizable by using
detuned Fabry-Perot cavities as input/output filters. At high frequencies, the
two schemes are shown to be equivalent, while at low frequencies our scheme
gives better performance than that of Harms et al., and is nearly fully
optimal. We then study the sensitivity improvement achievable by these schemes
in Advanced LIGO era (with 30-m filter cavities and current estimates of
filter-mirror losses and thermal noise), for neutron star binary inspirals, and
for narrowband GW sources such as low-mass X-ray binaries and known radio
pulsars. Optical losses are shown to be a major obstacle for the actual
implementation of these techniques in Advanced LIGO. On time scales of
third-generation interferometers, like EURO/LIGO-III (~2012), with
kilometer-scale filter cavities, a signal-recycling interferometer with the FD
readout scheme explored in this paper can have performances comparable to
existing proposals. [abridged]Comment: Figs. 9 and 12 corrected; Appendix added for narrowband data analysi
Search for gravitational wave bursts in LIGO's third science run
We report on a search for gravitational wave bursts in data from the three
LIGO interferometric detectors during their third science run. The search
targets subsecond bursts in the frequency range 100-1100 Hz for which no
waveform model is assumed, and has a sensitivity in terms of the
root-sum-square (rss) strain amplitude of hrss ~ 10^{-20} / sqrt(Hz). No
gravitational wave signals were detected in the 8 days of analyzed data.Comment: 12 pages, 6 figures. Amaldi-6 conference proceedings to be published
in Classical and Quantum Gravit
Quantum state preparation and macroscopic entanglement in gravitational-wave detectors
Long-baseline laser-interferometer gravitational-wave detectors are operating
at a factor of 10 (in amplitude) above the standard quantum limit (SQL) within
a broad frequency band. Such a low classical noise budget has already allowed
the creation of a controlled 2.7 kg macroscopic oscillator with an effective
eigenfrequency of 150 Hz and an occupation number of 200. This result, along
with the prospect for further improvements, heralds the new possibility of
experimentally probing macroscopic quantum mechanics (MQM) - quantum mechanical
behavior of objects in the realm of everyday experience - using
gravitational-wave detectors. In this paper, we provide the mathematical
foundation for the first step of a MQM experiment: the preparation of a
macroscopic test mass into a nearly minimum-Heisenberg-limited Gaussian quantum
state, which is possible if the interferometer's classical noise beats the SQL
in a broad frequency band. Our formalism, based on Wiener filtering, allows a
straightforward conversion from the classical noise budget of a laser
interferometer, in terms of noise spectra, into the strategy for quantum state
preparation, and the quality of the prepared state. Using this formalism, we
consider how Gaussian entanglement can be built among two macroscopic test
masses, and the performance of the planned Advanced LIGO interferometers in
quantum-state preparation
Searching for a Stochastic Background of Gravitational Waves with LIGO
The Laser Interferometer Gravitational-wave Observatory (LIGO) has performed
the fourth science run, S4, with significantly improved interferometer
sensitivities with respect to previous runs. Using data acquired during this
science run, we place a limit on the amplitude of a stochastic background of
gravitational waves. For a frequency independent spectrum, the new limit is
. This is currently the most sensitive
result in the frequency range 51-150 Hz, with a factor of 13 improvement over
the previous LIGO result. We discuss complementarity of the new result with
other constraints on a stochastic background of gravitational waves, and we
investigate implications of the new result for different models of this
background.Comment: 37 pages, 16 figure
The state of the Martian climate
60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes
Status Update and Interim Results from the Asymptomatic Carotid Surgery Trial-2 (ACST-2)
Objectives: ACST-2 is currently the largest trial ever conducted to compare carotid artery stenting (CAS) with carotid endarterectomy (CEA) in patients with severe asymptomatic carotid stenosis requiring revascularization. Methods: Patients are entered into ACST-2 when revascularization is felt to be clearly indicated, when CEA and CAS are both possible, but where there is substantial uncertainty as to which is most appropriate. Trial surgeons and interventionalists are expected to use their usual techniques and CE-approved devices. We report baseline characteristics and blinded combined interim results for 30-day mortality and major morbidity for 986 patients in the ongoing trial up to September 2012. Results: A total of 986 patients (687 men, 299 women), mean age 68.7 years (SD ± 8.1) were randomized equally to CEA or CAS. Most (96%) had ipsilateral stenosis of 70-99% (median 80%) with contralateral stenoses of 50-99% in 30% and contralateral occlusion in 8%. Patients were on appropriate medical treatment. For 691 patients undergoing intervention with at least 1-month follow-up and Rankin scoring at 6 months for any stroke, the overall serious cardiovascular event rate of periprocedural (within 30 days) disabling stroke, fatal myocardial infarction, and death at 30 days was 1.0%. Conclusions: Early ACST-2 results suggest contemporary carotid intervention for asymptomatic stenosis has a low risk of serious morbidity and mortality, on par with other recent trials. The trial continues to recruit, to monitor periprocedural events and all types of stroke, aiming to randomize up to 5,000 patients to determine any differential outcomes between interventions. Clinical trial: ISRCTN21144362. © 2013 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved
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