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  • 1
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    Multifactorial roles of interannual variability, season and sex for foraging patterns in a sexually size monomorphic seabird, the Australasian gannet (Morus serrator) (2018)
    Springer
    In:  Marine Biology, 165 . Art.Nr. 72.
    Details
    Publication Date: 2021-02-08
    Description: Marine top predators forage in environments that show potentially extreme temporal and spatial variation in prey availability, with reproductive success being crucially linked to food supply. Multiple factors of interannual and sexual variation, as well as variation across breeding stages, can shape patterns of spatial use in foraging seabirds, yet studies that address all of these variables simultaneously are rare. We present spatial assessment of foraging patterns by µGPS tracking of a sexually size monomorphic, long-lived species, the Australasian gannet (Morus serrator). The study spanned the incubation and chick-rearing stages in three consecutive breeding seasons. Our findings revealed high interannual variability in foraging distances and trip durations, but no consistent differences between birds across different breeding stages or the sexes. The exception was that core foraging areas were different for female and male Australasian gannets, although trip durations or distances were similar for both sexes. Our results also indicate bimodality in foraging distance and trip duration in this species, while highlighting interannual variability in the extent of bimodality. These findings contribute to a scarcely documented type of foraging behaviour in the seabird family of the Sulidae. Overall, these spatial use patterns provide a baseline for understanding the evolution of sex-specific foraging differences in biparental seabirds, and the extent to which these differences might help in securing breeding success across years of variable food availability.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00227-018-3332-0
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Widespread gene flow between oceans in a pelagic seabird species complex (2017)
    Wiley
    In:  Molecular Ecology, 26 (20). pp. 5716-5728.
    Details
    Publication Date: 2020-10-20
    Description: Global-scale gene flow is an important concern in conservation biology as it has the potential to either increase or decrease genetic diversity in species and populations. Although many studies focus on the gene flow between different populations of a single species, the potential for gene flow and introgression between species is understudied, particularly in seabirds. The only well-studied example of a mixed-species, hybridizing population of petrels exists on Round Island, in the Indian Ocean. Previous research assumed that Round Island represents a point of secondary contact between Atlantic (Pterodroma arminjoniana) and Pacific species (Pterodroma neglecta and Pterodroma heraldica). This study uses microsatellite genotyping and tracking data to address the possibility of between-species hybridization occurring outside the Indian Ocean. Dispersal and gene flow spanning three oceans were demonstrated between the species in this complex. Analysis of migration rates estimated using bayesass revealed unidirectional movement of petrels from the Atlantic and Pacific into the Indian Ocean. Conversely, structure analysis revealed gene flow between species of the Atlantic and Pacific oceans, with potential three-way hybrids occurring outside the Indian Ocean. Additionally, geolocation tracking of Round Island petrels revealed two individuals travelling to the Atlantic and Pacific. These results suggest that interspecific hybrids in Pterodroma petrels are more common than was previously assumed. This study is the first of its kind to investigate gene flow between populations of closely related Procellariiform species on a global scale, demonstrating the need for consideration of widespread migration and hybridization in the conservation of threatened seabirds.
    Type: Article , PeerReviewed
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    DOI: 10.1111/mec.14330
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    First genetic quantification of sex- and stage-specific feeding in the ubiquitous copepod Acartia tonsa (2018)
    Springer
    In:  Marine Biology, 165 (2). Art.No. 25.
    Details
    Publication Date: 2021-02-08
    Description: Marine copepods provide the major food-web link between primary producers and higher trophic levels, and their feeding ecology is of acute interest in light of global change impacts on food-web functioning. Recently, quantitative polymerase chain reaction (qPCR) protocols have been developed, which can complement classic diet quantification methods, such as stable isotope or fatty acid analyses tools. Here, we present first results of feeding experiments assessing sex- and stage-specific food intake by the ubiquitous calanoid copepod Acartia tonsa by 18S targeted qPCR and microscopic grazing assessment. In triplicated mixed-diet feeding treatments, three suitable A. tonsa diets, the cryptophyte Rhodomonas balthica, the haptophyte Isochrysis galbana, and the diatom Thalassiosira weissflogii, were offered in equal biomass proportions under constant conditions. Prey uptake substantially varied between different algal species, as did the extent of sex- and stage-specificity of prey uptake. Male adult copepods had higher R. balthica gut contents than females, and nauplii contained more of this prey source than copepodites or adult copepods in mixed treatments. A trend towards higher amounts of ingested T. weissflogii in adult females than in males and in nauplii than in other stages was detected. Genetic gut content quantifications indicated low feeding on I. galbana, and no consistent sex- or stage-specific differences of I. galbana content in A. tonsa. Our results highlight diet-specific feeding differences between Acartia life stages and sexes, which can have implications on food-web dynamics and specific nutrient transfer to higher trophic levels in copepod populations of varying age composition under changing environmental parameters, such as rising temperatures and increasing ocean acidification.
    Type: Article , PeerReviewed
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    DOI: 10.1007/s00227-017-3281-z
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    A virgin flight across the Tasman Sea? Satellite tracking of post-fledging movement in the Australasian Gannet Morus serrator (2010)
    Springer
    In:  Journal of Ornithology, 151 (3). pp. 755-759.
    Details
    Publication Date: 2020-07-20
    Description: New technologies enable tracking of the route, duration, and destination of previously unassessed long-distance movements. Fledgling Australasian Gannets Morus serrator from breeding populations in New Zealand had been reported to fly across the Tasman Sea to Australia, with this historic knowledge derived from the recovery of banded carcasses and from observations of initial flight direction. We deployed Argos satellite devices on ten M. serrator fledglings at Cape Kidnappers Gannetry, North Island, New Zealand, across 2 years. Birds that were tracked leaving the colony initially appeared to have landed on the sea. A male bird and two female birds were tracked moving along the east coast to the south tip of New Zealand. The two females then crossed the Tasman Sea to eastern Australian coastal waters in 4 and 5 days, respectively. We suggest that, contrary to historic reports, the route via Stewart Island constitutes a realized migration path for fledglings from Cape Kidnappers, which might minimize the distance traveled across the open sea to southeastern Australia or Tasmania. Our results further imply that initial direction of flight needs not be indicative of the subsequent migration route taken by M. serrator. This highlights the importance of direct tracking technology for adequate assessment of dispersal and migration in seabirds and other highly mobile species.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s10336-010-0504-1
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Size dimorphism and avian-perceived sexual dichromatism in a New Zealand endemic bird, the whiteheadMohoua albicilla (2010)
    Wiley
    In:  Journal of Morphology, 271 (6). pp. 697-704.
    Details
    Publication Date: 2020-07-22
    Description: Sex differences in behavior, morphology, and physiology are common in animals. In many bird species, differences in the feather colors of the sexes are apparent when judged by human observers and using physical measures of plumage reflectance, cryptic (to human) plumage dichromatism has also been detected in several additional avian lineages. However, it remains to be confirmed in almost all species whether sexual dichromatism is perceivable by individuals of the studied species. This latter step is essential because it allows the evaluation of alternative hypotheses regarding the signaling and communication functions of plumage variation. We applied perceptual modeling of the avian visual system for the first time to an endemic New Zealand bird to provide evidence of subtle but consistent sexual dichromatism in the whitehead, Mohoua albicilla. Molecular sexing techniques were also used in this species to confirm the extent of the sexual size dimorphism in plumage and body mass. Despite the small sample sizes, we now validate previous reports based on human perception that in male whiteheads head and chest feathers are physically brighter than in females. We further suggest that the extent of sexual plumage dichromatism is pronounced and can be perceived by these birds. In contrast, although sexual dimorphism was also detectable in the mass among the DNA-sexed individuals, it was found to be less extensive than previously thought. Sexual size dimorphism and intraspecifically perceivable plumage dichromatism represent reliable traits that differ between female and male whiteheads. These traits, in turn, may contribute to honest communication displays within the complex social recognition systems of communally breeding whitehead and other group-breeding taxa
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/jmor.10827
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Brood patch and sex-ratio observations indicate breeding provenance and timing in New Zealand storm petrel (Fregetta maoriana) (2013)
    Marine Ornithology
    In:  Marine Ornithology, 41 . pp. 107-111.
    Details
    Publication Date: 2017-10-10
    Description: We used measurements of brood patch and moult status to estimate the breeding phenology of New Zealand Storm-Petrel, using birds caught at sea within the Hauraki Gulf Marine Park near Auckland, New Zealand. Birds caught October–January had completely downy brood patches, whereas birds caught February–April had bare brood patches with an observed male bias in the February sex-ratio, consistent with a female pre-laying exodus typical of petrels and with the existence of an unknown colony in the region. No birds captured exhibited primary moult, which is known to occur in storm-petrels during their non-breeding season. Our data support the conclusion that the New Zealand storm-petrel breeds during January–June in northern New Zealand and that field surveys for the species on offshore islands in this region during this period are warranted
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Mate replacement entails a fitness cost for a socially monogamous seabird (2010)
    Springer
    In:  Naturwissenschaften, 97 (1). pp. 109-113.
    Details
    Publication Date: 2020-06-22
    Description: Studies of the selective advantages of divorce in socially monogamous bird species have unravelled extensive variation among different lineages with diverse ecologies. We quantified the reproductive correlates of mate retention, mate loss and divorce in a highly philopatric, colonially breeding biparental seabird, the Australasian gannet Morus serrator. Estimates of annual divorce rates varied between 40-43% for M. serrator and were high in comparison with both the closely related Morus bassanus and the range of divorce rates reported across monogamous avian breeding systems. Mate retention across seasons was related to consistently higher reproductive success compared with mate replacement, while divorce per se contributed significantly to lower reproductive output only in one of two breeding seasons. Prior reproductive success was not predictive of mate replacement overall or divorce in particular. These patterns are in accordance with the musical chairs hypothesis of adaptive divorce theory, which operates in systems characterised by asynchronous territorial establishment.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00114-009-0618-6
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Climate change affects low trophic level marine consumers: warming decreases copepod size and abundance (2015)
    Springer
    In:  Oecologia, 177 (3). pp. 849-860.
    Details
    Publication Date: 2017-04-13
    Description: Concern about climate change has re-ignited interest in universal ecological responses to temperature variations: (1) biogeographical shifts, (2) phenology changes, and (3) size shifts. In this study we used copepods as model organisms to study size responses to temperature because of their central role in the pelagic food web and because of the ontogenetic length constancy between molts, which facilitates the definition of size of distinct developmental stages. In order to test the expected temperature-induced shifts towards smaller body size and lower abundances under warming conditions, a mesocosm experiment using plankton from the Baltic Sea at three temperature levels (ambient, ambient +4 °C, ambient −4 °C) was performed in summer 2010. Overall copepod and copepodit abundances, copepod size at all life stages, and adult copepod size in particular, showed significant temperature effects. As expected, zooplankton peak abundance was lower in warm than in ambient treatments. Copepod size-at-immature stage significantly increased in cold treatments, while adult size significantly decreased in warm treatments.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00442-014-3130-4
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Evaluating on-land capture methods for monitoring a recently rediscovered seabird, the New Zealand Storm-Petrel Fregetta maoriana (2015)
    Marine Ornithology
    In:  Marine Ornithology, 43 (2). pp. 255-258.
    Details
    Publication Date: 2017-10-10
    Description: We provide a first assessment of various on-land capture methods for a procellarid seabird, the New Zealand Storm-Petrel Fregetta maoriana, which had been presumed extinct but for which a breeding site has just been discovered on Little Barrier Island. In the vicinity of an active breeding site, playback only, also involving a newly isolated call from in situ deployed sound-recording devices, could efficiently be employed for capture, while light attraction in combination with playback achieved comparable capture success further afield. We consider that these findings can be relevant for breeding ground searches and capture operations in other storm-petrel species, and more generally in seabirds that visit their breeding sites at night.
    Type: Article , PeerReviewed
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    Is the chemical composition of biomass the agent by which ocean acidification impacts on zooplankton ecology? (2017)
    Springer
    In:  Aquatic Sciences, 79 (3). pp. 733-748.
    Details
    Publication Date: 2020-02-06
    Description: Climate change impacts prevail on marine pelagic systems and food webs, including zooplankton, the key link between primary producers and fish. Several metabolic, physiological, and ecological responses of zooplankton species and communities to global stressors have recently been tested, with an emerging field in assessing effects of combined climate-related factors. Yet, integrative studies are needed to understand how ocean acidification interacts with global warming, mediating zooplankton body chemistry and ecology. Here, we tested the combined effects of global warming and ocean acidification, predicted for the year 2100, on a community of calanoid copepods, a ubiquitously important mesozooplankton compartment. Warming combined with tested pCO2 increase affected metabolism, altered stable isotope composition and fatty acid contents, and reduced zooplankton fitness, leading to lower copepodite abundances and decreased body sizes, and ultimately reduced survival. These interactive effects of temperature and acidification indicate that metabolism-driven chemical responses may be the underlying correlates of ecological effects observed in zooplankton communities, and highlight the importance of testing combined stressors with a regression approach when identifying possible effects on higher trophic levels.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00027-017-0532-5
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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