The Tahiti petrel (Pseudobulweria rostrata) is a rare and declining seabird whose breeding biology and nest-site selection are poorly known. Nest-site selection is critical to seabird population ...fitness, and understanding the factors driving it is essential for designing effective conservation measures. Here, we measured several variables (topographical, physical and environmental) to characterize Tahiti petrel nesting habitats and burrows (i.e., width, height, depth and type: rocky cavity, dug into the soil or under a root) on Nemou Island in New Caledonia. The data were clustered using the HCPC (Hierarchical Clustering on Principal Component) method to identify principal habitat groups. This method was combined with logistic regressions to examine the influence of the variables on nest-site selection and breeding success. Our results showed that nest-site selection is linked to habitat groups (a combination of substrate and vegetation data), slope, orientation and soil depth, while breeding success is only influenced by nest characteristics (i.e., burrow type and width). Tahiti petrels prefer to nest on steep slopes in mature forests with rocky substrate and deep soil. Burrows were scatterred in small sub-colonies or isolated pairs, suggesting that nest-site selection depends on habitat quality rather than conspecific density. The study also revealed that breeding success is lower in rocky cavities and increases in burrows with wide entrances. Our nest-site selection survey is the first for the genus Pseudobulweria, and provides critical information for designing effective conservation programs in New Caledonia and the Pacific.
Lunar phase and illumination are known to affect nocturnal behavior of many organisms, particularly through predator-prey interactions. Visual predators can benefit from higher light levels to ...increase their activity, while prey may decrease their activity to avoid predation. The lower number of nocturnal seabirds observed on colonies during full moon nights has been mostly interpreted as a predation avoidance strategy. However, it is also possible that shearwaters take advantage of the moon's illumination to feed also at night, and stay at sea to forage during full moon nights. We used miniaturized GPS-loggers to obtain 179 tracks from 99 wedge-tailed shearwaters breeding in New Caledonia, to investigate moonlight effects on individual behavior. Lunar phase significantly predicted self-provisioning trip duration, with individuals performing longer trips around the full moon. However, this relationship was not significant during chick-provisioning trips when adults have to frequently return to the colony. Adults mostly returned to the colony during moonlit periods, refuting the predation avoidance theory. Tracked individuals showed an unexpectedly high amount of nocturnal foraging activity (28% of total activity), positively influenced by the presence of the moon. δ15N stable isotope values were significantly related to the percentage of nocturnal foraging, but with a weak relationship, impeding our ability to confirm that wedge-tailed shearwaters fed on different prey when foraging at night. This study suggests that reduced colony attendance around the full moon may be linked to greater at-sea foraging opportunities in distant oceanic areas than to increased predation risk on land.
•Nocturnal Procellariids decrease their activity on colonies around the full moon.•It has been previously interpreted as predation avoidance.•Here, wedge-tailed shearwaters returned to the colony mostly during the moonlit period of the night.•They foraged more intensively at night under moonlit conditions.•Decreased activity at the colony may be rather due to higher foraging efficiency of seabirds around the full moon.
The ability of corals to modulate their nutrition strategy in response to variable nutrient supply remains poorly understood, limiting our understanding of energy flow in coral reef ecosystems and ...thus our comprehension of their resilience to global changes. We used a naturally occurring nutrient gradient along the reef flat of two seabird-inhabited islets in the SW Pacific to characterize spatiotemporal fluctuations in coastal nutrient availability, and how it modulates the trophic response of the mixotrophic coral
Pocillopora damicornis
. The clear gradients in dissolved NOx and δ
15
N values of macroalgae and both
P. damicornis
tissues and symbionts observed along the reef flat during the dry and the rainy season revealed that seabird-derived-N is supplied year-round to the reef flat. Yet, nitrogen isotope values of macroalgae show that the seabirds’ effect on coral reefs varies with sites and seasons. Metrics derived from the SIBER framework revealed that coral nutrition seasonally favored autotrophy when exposed to higher seabird guano concentrations and at inshore stations, while heterotrophy dominated in corals less exposed to seabird-derived nutrient supply.
P. Damicornis
is therefore able to cope with large changes in nitrogen supply induced by seabird island communities by switching between autotrophy and heterotrophy. These results shed light on the flexibility of resource sharing within the coral-algae symbiosis and highlight the importance of seabird populations to the functioning of coral reef ecosystems.
Reef-building corals generally thrive in nutrient-poor tropical waters, where among other elements, nitrogen (N) availability often limits primary productivity. In addition to their close association ...with endosymbiotic dinoflagellates of the family Symbiodiniaceae, enabling an effective use and retention of dissolved inorganic nitrogen (DIN), scleractinian corals have developed strategies to acquire new N: (1) They can ingest N-rich sediment particles and preys (from picoplankton to macro-zooplankton) via heterotrophy, including diazotrophs plankton fixing dinitrogen (N
2
) and releasing part of this nitrogen—Diazotroph-Derived N (DDN)—in seawater, a pathway called “heterotrophic nutrition on diazotrophs”; (2) Symbiotic diazotrophs located in the coral holobiont have the molecular machinery to fix N
2
, a pathway called “symbiotic N
2
fixation”. Here we used the
15
N
2
isotopic labeling in a series of incubations to investigate the relative contribution of each of these DDN transfer pathways in three worldwide distributed coral species:
Acropora muricata
,
Galaxea fascicularis, and Pocillopora damicornis
. We show that N provision via “symbiotic N
2
fixation” is negligible compared to that obtained via “heterotrophic nutrition on diazotrophs,” with DDN assimilation rates about a thousand times lower for
P. damicornis
and
G. fascicularis
, or assimilation rates via “symbiotic N
2
fixation” almost nil for
A. muricata
. Through heterotrophic feeding on planktonic diazotrophs, only
G. fascicularis
and
P. damicornis
can successfully obtain N and fulfill a large part of their N requirements (DDN asimilation rates: 0.111 ± 0.056 and 0.517 ± 0.070 μg N cm
–2
h
–1
in their Symbiodiniaceae, respectively). Whereas this contribution is again negligible for
A. muricata
. They also largely consume the picoplankton that likely benefit from this DDN (
Prochlorococcus
and
Synechococcus
cells; respectively, 2.56 ± 1.57 10
4
and 2.70 ± 1.66 10
4
cell h
–1
cm
–2
for
G. fascicularis
; 3.02 ± 0.19 10
5
and 1.14 ± 0.79 10
4
cell h
–1
cm
–2
for
P. damicornis
). The present study confirms the different dependencies of the three tested species regarding heterotrophy, with
P. damicornis
and
G. fascicularis
appearing highly efficient at capturing plankton, while
A. muricata
, considered as mainly autotroph, does not rely on these food resources to meet its N and energy needs.
Seabirds have been particularly affected by invasive non‐native species, which has led to the implementation of numerous eradication campaigns for the conservation of these keystone and highly ...vulnerable species. Although the benefits of eradication of invasive non‐native species for seabird conservation have been demonstrated, the recovery kinetics of different seabird populations on islands after eradication remains poorly evaluated. We conducted long‐term monitoring of the number of breeding pairs of seven seabird species on a small atoll, Surprise Island, New Caledonia (southwestern tropical Pacific). Marine avifauna of the island were surveyed yearly 4 years before to 4 years after rodent eradication (conducted in 2005), and we conducted multiple one‐time surveys from ∼10 years before and ∼15 years after eradication. We sought to determine how different seabird species responded to the eradication of invasive rodents in an insular environment. Three species responded positively (two‐ to 10‐fold increase in population size) to eradication with differences in lag time and sensitivity. The number of breeding pairs increased (effect sizes = 0.49–0.95 and 0.35–0.52) for two species over 4 years post‐eradication due to immigration. One species had a longer (at least 5 years) response time than all others; breeding pairs increased for over 10 years after eradication. Long‐term sampling was necessary to observe the responses of the seabird populations on the island because of the delayed response of a species to eradication not visible in the first years after eradication. Our results confirmed the positive effects of eradication of invasive non‐native species on seabirds and emphasize the importance of mid‐ and long‐term pre‐ and posteradication surveys to decipher the mechanisms of seabird recovery and confirm the benefits of eradication for conservation purposes.
Resumen
Las especies invasoras no nativas han afectados en lo particular a las aves marinas, lo que ha derivado en la implementación de numerosas campañas de eliminación para conservar estas especies importantes y muy vulnerables. Aunque se han demostrado los beneficios de la eliminación de especies invasoras no nativas para la conservación de las aves marinas, se conoce poco sobre la cinética de la recuperación de las diferentes poblaciones insulares después de la eliminación. Realizamos un monitoreo a largo plazo del número de parejas reproductoras de siete especies de aves marinas en Isla Surprise, Nueva Caledonia, un atolón pequeño en el suroeste del Pacífico tropical. Censamos anualmente la avifauna marina de la isla cuatro años antes y cuatro años después de la eliminación de roedores (realizada en 2005) y realizamos varios censos únicos de ∼10 años antes y ∼15 años después de la eliminación. Buscamos determinar cómo las diferentes especies de aves marinas respondían a la eliminación de los roedores invasores en un ambiente insular. Tres especies respondieron positivamente (un incremento poblacional de 2 a 10 veces mayor) a la eliminación con diferencias en el tiempo de desfase y en la sensibilidad. El número de parejas reproductoras incrementó (tamaños eficientes = 0.49 a 0.95 y 0.35 a 0.52) para dos especies cuatro años después de la eliminación debido a la inmigración. Una especie tuvo un tiempo de respuesta más largo (al menos cinco años) que las demás; las parejas reproductoras incrementaron más de diez años después de la eliminación. El muestreo a largo plazo fue necesario para observar las respuestas de las poblaciones de aves marinas en la isla porque una especie tuvo una respuesta retardada que no fue visible en los primeros años después de la eliminación. Nuestros resultados confirmaron los efectos positivos que tiene la eliminación de especies invasoras no nativas sobre las aves marinas y recalca la importancia de los censos a mediano y largo plazo antes y después de la eliminación para identificar los mecanismos de la recuperación poblacional y confirmar los beneficios con fines de conservación que tiene este método.
Recuperación de las poblaciones de aves marinas insulares años después de la eliminación de roedores
Long-term monitoring of seabird dynamics on Surprise Island highlights the benefits of rodent eradication on seabird population recovery.
Resumen Las especies invasoras no nativas han afectados en lo ...particular a las aves marinas, lo que ha derivado en la implementación de numerosas campañas de eliminación para conservar estas especies importantes y muy vulnerables. Aunque se han demostrado los beneficios de la eliminación de especies invasoras no nativas para la conservación de las aves marinas, se conoce poco sobre la cinética de la recuperación de las diferentes poblaciones insulares después de la eliminación. Realizamos un monitoreo a largo plazo del número de parejas reproductoras de siete especies de aves marinas en Isla Surprise, Nueva Caledonia, un atolón pequeño en el suroeste del Pacífico tropical. Censamos anualmente la avifauna marina de la isla cuatro años antes y cuatro años después de la eliminación de roedores (realizada en 2005) y realizamos varios censos únicos de ∼10 años antes y ∼15 años después de la eliminación. Buscamos determinar cómo las diferentes especies de aves marinas respondían a la eliminación de los roedores invasores en un ambiente insular. Tres especies respondieron positivamente (un incremento poblacional de 2 a 10 veces mayor) a la eliminación con diferencias en el tiempo de desfase y en la sensibilidad. El número de parejas reproductoras incrementó (tamaños eficientes = 0.49 a 0.95 y 0.35 a 0.52) para dos especies cuatro años después de la eliminación debido a la inmigración. Una especie tuvo un tiempo de respuesta más largo (al menos cinco años) que las demás; las parejas reproductoras incrementaron más de diez años después de la eliminación. El muestreo a largo plazo fue necesario para observar las respuestas de las poblaciones de aves marinas en la isla porque una especie tuvo una respuesta retardada que no fue visible en los primeros años después de la eliminación. Nuestros resultados confirmaron los efectos positivos que tiene la eliminación de especies invasoras no nativas sobre las aves marinas y recalca la importancia de los censos a mediano y largo plazo antes y después de la eliminación para identificar los mecanismos de la recuperación poblacional y confirmar los beneficios con fines de conservación que tiene este método. Recuperación de las poblaciones de aves marinas insulares años después de la eliminación de roedores
The increasing use of, and visits to, isolated territories by people (especially tourists) enables the investigation of how biodiversity reacts to evolutionarily novel pressures. We explored the ...behavioural reaction of a breeding seabird species, the Brown Noddy Anous stolidus, to our repeated visits at two study sites in the Chesterfield Islands, a newly classified reserve in the Coral Sea Natural Park. Repeated measures of flight‐initiation distances (FIDs) at three sites and over time suggest that human visitations induced both a spatial phenotypical sorting or learning of individuals and a temporal habituation. In light of the novel ‘Sit and Defend’ mode of avian nest defence, the study finally provides the first dataset of FIDs for this species, and highlights management opportunities that could arise from the replication of such an approach to other breeding seabirds and therefore the conservation of remote island ecosystems.
Understanding the ecological mechanisms underpinning distribution patterns is vital in managing populations of mobile marine species. This study is a first step towards an integrated description of ...the habitats and spatial distributions of marine predators in the Natural Park of the Coral Sea, one of the world’s largest marine-protected areas at about 1.3 million km
2
, covering the entirety of New Caledonia’s pelagic waters. The study aims to quantify the benefit of including a proxy for prey abundance in predator niche modelling, relative to other marine physical variables. Spatial distributions and relationships with environmental data were analysed using catch per unit of effort data for three fish species (albacore tuna, yellowfin tuna and dolphinfish), sightings collected from aerial surveys for three cetacean guilds (Delphininae, Globicephalinae and Ziphiidae) and foraging locations identified from bio-tracking for three seabird species (wedge-tailed shearwater, Tahiti petrel and red-footed booby). Predator distributions were modelled as a function of a static covariate (bathymetry), oceanographic covariates (sea surface temperature, chlorophyll-
a
concentration and 20 °C-isotherm depth) and an acoustically derived micronekton preyscape covariate. While distributions were mostly linked to bathymetry for seabirds, and chlorophyll and temperature for fish and cetaceans, acoustically derived prey abundance proxies slightly improved distribution models for all fishes and seabirds except the Tahiti petrel, but not for the cetaceans. Predicted spatial distributions showed that pelagic habitats occupied by predator fishes did not spatially overlap. Finally, predicted habitats and the use of the preyscapes in predator habitat modelling were discussed.
Understanding the ecological mechanisms underpinning distribution patterns is vital in managing populations of mobile marine species. This study is a first step towards an integrated description of ...the habitats and spatial distributions of marine predators in the Natural Park of the Coral Sea, one of the world’s largest marine-protected areas at about 1.3 million km², covering the entirety of New Caledonia’s pelagic waters. The study aims to quantify the benefit of including a proxy for prey abundance in predator niche modelling, relative to other marine physical variables. Spatial distributions and relationships with environmental data were analysed using catch per unit of effort data for three fish species (albacore tuna, yellowfin tuna and dolphinfish), sightings collected from aerial surveys for three cetacean guilds (Delphininae, Globicephalinae and Ziphiidae) and foraging locations identified from bio-tracking for three seabird species (wedge-tailed shearwater, Tahiti petrel and red-footed booby). Predator distributions were modelled as a function of a static covariate (bathymetry), oceanographic covariates (sea surface temperature, chlorophyll-a concentration and 20 °C-isotherm depth) and an acoustically derived micronekton preyscape covariate. While distributions were mostly linked to bathymetry for seabirds, and chlorophyll and temperature for fish and cetaceans, acoustically derived prey abundance proxies slightly improved distribution models for all fishes and seabirds except the Tahiti petrel, but not for the cetaceans. Predicted spatial distributions showed that pelagic habitats occupied by predator fishes did not spatially overlap. Finally, predicted habitats and the use of the preyscapes in predator habitat modelling are discussed.
The wedge-tailed shearwater (WTS) population of New Caledonia is one of the largest in the world, yet its biology and foraging ecology are poorly known. We studied WTS from 4 colonies in New ...Caledonia.We examined foraging behaviour and habitats using GPS receivers and light sensors during and outside the breeding season, respectively, and compared our findings with those from other WTS populations worldwide. During breeding, New Caledonian WTS alternated short foraging trips close to the colony over the lagoon, or off the reef edge, with longer trips over distant, deep waters. Whereas neighboring colonies overlapped at sea, especially during short trips, there was a clear separation of foraging zones between the pairs of colonies located in the southern versus northwestern parts of New Caledonia. Although WT Sactively foraged and commuted to foraging zones during the day, they mainly returned to the colony or rested at night, indicating that they feed mainly during the day. Active foraging did not take place in more productive areas, suggesting that it may instead be related to the presence of sub-surface predators. Outside the breeding season, birds from 3 colonies had similar trans-equatorial migratory behaviour. All left New Caledonia at the same time of the year with a fast, northeasterly movement and wintered over deep waters in the same sector of the northwestern tropical Pacific Ocean. At overwintering sites, they spent most of their non-foraging time presumably sitting on the water, especially at night, making a slow westward movement before returning to New Caledonia. WTS from New Caledonia forage over warm, oligotrophic deep waters throughout their life cycle, and the species appears to have a flexible foraging strategy adapted to the various environmental conditions encountered across its wide tropical range.
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