Westland petrel (Procellaria westlandica) foraging behaviour: Patterns and drivers of individual variation

<p><b>Foraging behaviour can have a major influence on the survival and reproduction of individuals which can ultimately impact the viability of a population. Foraging is particularly challenging for procellariiformes (tube nosed seabirds) who feed on patchily distributed prey in the highly dynamic marine environment. During the breeding season procellariiformes must also increase their foraging effort to raise their chick whilst having a reduced foraging range. As a result, procellariiformes have adopted various foraging strategies, such as dual foraging and sexual foraging dimorphism, to cope with this energy demanding lifestyle. Westland petrels (Procellaria westlandica) are an endangered winter breeding procellariform endemic to the West Coast of New Zealand’s South Island. Unlike other procellariiformes, previous studies have found little evidence of Westland petrels using sexually dimorphic or dual foraging strategies. Furthermore, Westland petrels also display a high level of individual variation in foraging behaviour. To understand why there is so much variation and what factors are driving it, I first examined variation at the population, individual and within individual level to describe and categorise different foraging strategies. I then investigated how factors such as year, sex and foraging site influenced variation. Finally, I examined how oceanic variables influenced habitat selection and foraging characteristics to understand how the environment drives variation in foraging behaviour.</b></p> <p>Considerable variation was found at all levels. Most of the variation was explained by year with individuals taking shorter foraging trips in 2011 and longer trips in 2015. Females foraged further than males suggesting that there is some degree of sexual foraging segregation occurring in Westland petrels. I also found that the highest variation in foraging behaviour was exhibited by individuals within their core foraging site on the West Coast. Sea surface temperatures were highest at the West Coast foraging site and individuals within this site showed differences in habitat selection among years. Habitat selection at the West Coast site also differed between sexes suggesting that males are outcompeting females for prime foraging spots.</p> <p>Overall, my results indicate that foraging conditions on the West Coast are highly variable likely due to rising sea surface temperatures, marine heatwaves, and the effects of the El Nino-Southern Oscillation. As a result, it is likely that prey availability on the West Coast is unpredictable causing high variation in foraging behaviour and sexual foraging segregation. With climate change, foraging conditions on the West Coast are predicted to get more unpredictable as sea surface temperatures continue to rise and extreme weather events become more frequent. These factors will make foraging increasingly difficult for Westland petrels and could see them rely more on fishery discards as a source of food, increasing their risk of incidental mortality. Conservation management should focus on protecting the petrels core foraging area around the Hokitika canyon to help limit the effects of climate change. Fishery management should also focus on limiting or prohibiting offal discards to prevent the incidental mortality of Westland petrels.</p>

Westland petrel (Procellaria westlandica) foraging behaviour: Patterns and drivers of individual variation

<p><b>Foraging behaviour can have a major influence on the survival and reproduction of individuals which can ultimately impact the viability of a population. Foraging is particularly challenging for procellariiformes (tube nosed seabirds) who feed on patchily distributed prey in the highly dynamic marine environment. During the breeding season procellariiformes must also increase their foraging effort to raise their chick whilst having a reduced foraging range. As a result, procellariiformes have adopted various foraging strategies, such as dual foraging and sexual foraging dimorphism, to cope with this energy demanding lifestyle. Westland petrels (Procellaria westlandica) are an endangered winter breeding procellariform endemic to the West Coast of New Zealand’s South Island. Unlike other procellariiformes, previous studies have found little evidence of Westland petrels using sexually dimorphic or dual foraging strategies. Furthermore, Westland petrels also display a high level of individual variation in foraging behaviour. To understand why there is so much variation and what factors are driving it, I first examined variation at the population, individual and within individual level to describe and categorise different foraging strategies. I then investigated how factors such as year, sex and foraging site influenced variation. Finally, I examined how oceanic variables influenced habitat selection and foraging characteristics to understand how the environment drives variation in foraging behaviour.</b></p> <p>Considerable variation was found at all levels. Most of the variation was explained by year with individuals taking shorter foraging trips in 2011 and longer trips in 2015. Females foraged further than males suggesting that there is some degree of sexual foraging segregation occurring in Westland petrels. I also found that the highest variation in foraging behaviour was exhibited by individuals within their core foraging site on the West Coast. Sea surface temperatures were highest at the West Coast foraging site and individuals within this site showed differences in habitat selection among years. Habitat selection at the West Coast site also differed between sexes suggesting that males are outcompeting females for prime foraging spots.</p> <p>Overall, my results indicate that foraging conditions on the West Coast are highly variable likely due to rising sea surface temperatures, marine heatwaves, and the effects of the El Nino-Southern Oscillation. As a result, it is likely that prey availability on the West Coast is unpredictable causing high variation in foraging behaviour and sexual foraging segregation. With climate change, foraging conditions on the West Coast are predicted to get more unpredictable as sea surface temperatures continue to rise and extreme weather events become more frequent. These factors will make foraging increasingly difficult for Westland petrels and could see them rely more on fishery discards as a source of food, increasing their risk of incidental mortality. Conservation management should focus on protecting the petrels core foraging area around the Hokitika canyon to help limit the effects of climate change. Fishery management should also focus on limiting or prohibiting offal discards to prevent the incidental mortality of Westland petrels.</p>

Distinct off-equatorial zonal wind stress and oceanic responses for EP and CP type ENSO events

This study utilises observations and a series of idealised experiments to explore whether Eastern Pacific (EP) and Central Pacific (CP) type El Niño-Southern Oscillation (ENSO) events produce surface wind stress responses with distinct spatial structures. We find that the meridionally broader sea surface temperatures (SST) during CP events lead to zonal wind stresses that are also meridionally broader than those found during EP type events, leading to differences in the near-equatorial wind stress curl. These wind spatial structure differences create differences in the associated pre- and post-ENSO event WWV response. For instance, the meridionally narrow winds found during EP events have: i) weaker wind stresses along 5°N and 5°S, leading to weaker Ekman induced pre-event WWV changes; and ii) stronger near-equatorial wind stress curls that lead to a much larger post-ENSO event WWV changes than during CP events. The latter suggests that, in the framework of the recharge oscillator model, the EP events have stronger coupling between sea surface temperatures (SST) and thermocline (WWV), supporting more clearly the phase transition of ENSO events, and therefore the oscillating nature of ENSO than CP events. The results suggest that the spatial structure of the SST pattern and the related differences in the wind stress curl, are required along with equatorial wind stress to accurately model the WWV changes during EP and CP type ENSO events.

Response of Tropical Cyclone Frequency to Sea Surface Temperatures Using Aqua-Planet Simulations

The present study investigates the effect of increasing sea surface temperatures (SSTs) on tropical cyclone (TC) frequency using the high-resolution Australian Community Climate and Earth-System Simulator (ACCESS) model. We examine environmental conditions leading to changes in TC frequency in aqua-planet global climate model simulations with globally uniform sea surface temperatures (SSTs). Two different TC tracking schemes are used. The Commonwealth Scientific and Industrial Research Organization (CSIRO) scheme (a resolution-dependent scheme) detects TCs that resemble observed storms, while the Okubo–Weiss zeta parameter (OWZP) tracking scheme (a resolution-independent scheme) detects the locations within “marsupial pouches” that are favorable for TC formation. Both schemes indicate a decrease in the global mean TC frequency with increased saturation deficit and static stability of the atmosphere. The OWZP scheme shows a poleward shift in the genesis locations with rising temperatures, due to lower vertical wind shear. We also observe an overall decrease in the formation of tropical depressions (TDs) with increased temperatures, both for those that develop into TCs and non-developing cases. The environmental variations at the time of TD genesis between the developing and the non-developing tropical depressions identify the Okubo–Weiss (OW) parameter and omega (vertical mass flux) as significant influencing variables. Initial vortices with lower vorticity or with weaker upward mass flux do not develop into TCs due to environments with higher saturation deficit and stronger static stability of the atmosphere. The latitudinal variations in the large-scale environmental conditions account for the latitudinal differences in the TC frequency in the OWZP scheme.

Recent winter warming over India – spatial and temporal characteristics of monthly maximum and minimum temperature trends for January to March

In the backdrop of recent warmer winters over India, temperature series of 174 stations well distributed over the country were statistically analyzed to document the long term variations and trends in monthly mean maximum and minimum temperatures for January to March. From the trend analysis, February month has emerged as the warmer winter month over North India where increase in both maximum (+0.29° C / decade) and minimum (+0.38° C / decade) temperatures is highest with noteworthy increase in maximum temperature at a rate 1.5 times that of the South India averaged increase. Spatially, North India minimum temperature trends for February and March and South India maximum temperature trends for all months are more coherent. Both day-time and night-time total cloud amounts are increasing significantly over Indo-Gangetic plains and south peninsula and decreasing significantly in central and east India. However increase in temperatures over extreme south peninsula in January and March is difficult to explain on the basis of increase in day-time total cloud amount indicating strong influence of other climatic factors. At the same time, sea surface temperatures of the Arabian Sea and the Bay of Bengal are rising and there is strong positive correlation between land surface temperatures and sea surface temperatures suggesting significant contribution of warmer sea waters which may have important climatic implications over neighbouring regions.

The Early Paleogene Succession at Tora, New Zealand; Stratigraphy and Paeloclimate: A Critical North Island Eocene Temperature Record and a Crucial Linkage Between the Depositional Settings of the Central and Southern East Coast Basin

<p>This study has utilised the Mg/Ca paleothermometry method to provide a new, North Island reference of sea temperatures in the Southwest Pacific during a period of extreme global warming, referred to as the Early Eocene Climatic Optimum (EECO; ~53-50 Ma). This period of Earth’s history is of great interest as it represents the warmest climates of the Cenozoic. Importantly the climate dynamics of this period as simulated by computer models do not appear to match paleo-proxy data, specifically with regard to the latitudinal distribution of heat. Development of this paleoceanographic record involved detailed mapping of three sections in the Wairarapa region (41.506199 S, 175.517663 E) of New Zealand’s North Island. Three primary stratigraphic sections (Pukemuri, Awheaiti and Te Oroi Streams) were described and dated using foraminiferal and calcareous nannofossil biostratigraphy, with supplementary observations and measurements included from sections at Manurewa and Te Kaukau Points. These sediments are primarily siliciclastic sandstones and mudstones in composition, and sedimentary structures within these sections include turbidite sequences, channelisation and synsedimentary slumping, suggesting the EECO interval here is represented by sedimentation within a mid-bathyal submarine channel and fan environment. In contrast, the Early Paleocene Manurewa and Awhea Formations have previously been interpreted as a shallow, marginal marine environment which is at odds with benthic foraminiferal paleodepth indicators and trace fossil assemblages identified in this study. Selected genera of planktic foraminifera were extracted from the EECO interval and paleo-water temperatures determined from Mg/Ca values measured by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA ICPMS). This method was selected as it allows specific targeting of analysis sites, enabling avoidance of contaminated and altered parts of the test. This method also provides simultaneous measurements of other trace elements (Al, Si, Ti, Mn, Zn, Sr, Ba) that can be used as a guide to preservation state of the test (for example, Al, Ti and Si are considered indicators of detrital contamination levels). Four foraminifera genera were selected as suitable paleotemperature indicators of separate components of the water column. Morozovella spp. and Acarinina spp. were selected for surface mixed layer paleotemperature estimates, Subbotina spp. for thermocline temperature values, and Cibicides spp. for bottom water temperature determinations.SEM images, combined with trace element data were used to parse the resulting Mg/Ca data and only those that met strict quality criterion, including low detrital contamination and lack of visual evidence for recrystalisation were used for temperature reconstruction. Planktic Mg/Ca data were converted to temperature using the relationship (Mg/Ca = [Mg/Casw-t]/[Mg/Casw-0] × 0.38 0.09 × T) and benthic Mg/Ca temperatures calculated using (Mg/Ca = [Mg/Casw-t]/[Mg/Casw-0] × 0.87 0.109 × T), each assuming an early Eocene seawater Mg/Ca value of 4.1 mol/mol. Calibrated Mg/Ca results show peak sea surface temperatures of 29°C for Morozovella and Acarinina in the East Coast Basin during the Early Eocene, with bottom water temperatures of 17°C obtained from Cibicides. These data are consistent with the high sea surface temperatures reconstructed by previous workers in the nearby Canterbury Basin. The data from this new reference point support the idea that the EECO was characterised by a lower, possibly absent latitudinal temperature gradient in the midlatitude Southwest Pacific, than numerical models suggest, indicating a fundamental gap in the knowledge of climate dynamics in conditions much warmer than today.</p>