At-sea Behaviour Research Articles

Boldness predicts foraging behaviour, habitat use and chick growth in a central place marine predator

Animal personality can shape individual’s fitness. Yet, the mechanistic relationship by which individual’s personality traits lead to variations in fitness remains largely underexplored. Here, we used novel object tests to measure boldness of chick-provisioning Cory’s shearwaters (Calonectris borealis) from a coastal colony off west Portugal, and deployed GPS loggers to study their at-sea behaviour and distribution. We then tested whether boldness predicts individual differences in adult’s trophic ecology and variations in chick growth, to assess potential implications of personality-specific foraging behaviours. Foraging effort was higher for shyer than for bolder individuals, which, during short forays, exhibited larger foraging ranges, and foraged in regions of higher and more variable bathymetry. This suggests that nearby the colony bolder individuals expanded their foraging area to maximize resource acquisition and increase the probability of foraging success. When endeavouring to longer distances, bolder individuals exhibited comparably shorter foraging ranges and targeted low bathymetry regions, likely with enhanced prey availability, while shyer individuals exhibited much larger foraging ranges indicating greater flexibility when foraging in oceanic realms. Despite such differences between bolder and shyer individuals their isotopic niches were similar. Yet, chicks raised by bolder parents grew at a faster rate than those raised by shyer parents. Together, our results suggest that differences in resource acquisition strategies could play a key role through which individual’s boldness may influence breeding performance, even when individuals have similar isotopic preferences.

The challenges of independence: ontogeny of at-sea behaviour in a long-lived seabird

The challenges of independence: ontogeny of at-sea behaviour in a long-lived seabird

Challenges in quantifying the responses of Black-legged Kittiwakes Rissa tridactyla to habitat variables and local stressors due to individual variation

ABSTRACT Capsule Strong individual variation was observed in the responses of Black-legged Kittiwakes Rissa tridactyla to environmental covariates related to foraging behaviour and habitat selection, and in the overlap with nearby offshore windfarms (OWFs). Aims To determine whether environmental covariates consistently drive Kittiwake foraging behaviour and how this may influence overlap with local potential stressors at the population and individual levels. Methods We used two complimentary methods (Hidden Markov Models and Step Selection Functions) to classify the at-sea behaviour of Kittiwakes and identify environmental covariates associated with foraging at a colony in northeast Scotland during the 2021 breeding season. We also calculated the overlap, by behaviour, of individuals with several operational and proposed OWFs within the vicinity. Results We found no evidence for habitat selection at the population level, with uncertainty in which conditions were linked to foraging, due to considerable variation in the responses of individuals to local environmental conditions. This was attributed to unmeasured intrinsic variation among individuals and high competition among conspecifics and other seabird species. We also observed variation among individuals in the extent of overlap with a local stressor, OWFs, by behaviour. Conclusion Individuals within a population that do not respond consistently to environmental conditions will likely vary in their vulnerability to local stressors, in this case to OWFs. This could lead to unforeseen population-level consequences if not accounted for. Therefore, it is important to identify and understand variation among individuals to better establish population-level consequences of different foraging areas and overlap with stressors to reduce uncertainty in current impact assessments.

The ontogeny of at-sea behaviour in male southern elephant seals (Mirounga leonina) at Marion Island

Megafauna, such as southern elephant seals (SESs) (Mirounga leonina, Linn.), forage in diverse, seemingly limitless habitats. In pelagic settings, their behaviour is more likely to be limited by physiological ability and prey distribution, than physical barriers. For elephant seals, their rapid growth in body size corresponds to changing physiological abilities. These changes are most pronounced for male elephant seals. While most studies have compared male and female SESs in terms of changing body size and physiological ability, few studies have compared the influence of changing body size on behaviour of male SESs from the same population using long term satellite tracking data. We describe age-related differences in movement and diving behaviour for male SESs from Marion Island. We analysed satellite tracking data collected from 23 male SESs seals fitted with Sea Mammal Research Unit Satellite Relay Data Loggers at Marion Island between 2005 and 2011. Each dive was assigned a behavioural mode, either ‘searching’ or ‘transit’, using state-space modelling. We used mixed-effects models to quantify the influence of age and behavioural mode on dive duration, surface duration, dive depth and number of daily dives. Younger seals travelled significantly further from Marion Island and spent most of their dives in transit mode, whereas older seals stayed closer to the island but were in searching mode for most of their tracks. When searching, older seals dived more frequently, displayed longer dive and surface durations, and reached greater depths than younger seals. These differences in diving behaviour seem to reflect changing physiological ability. For male SESs, changes in physiological ability necessitate behavioural plasticity, which may be the key to survival and future breeding success. Robust males are more likely to breed and must therefore, maintain their body size by adapting to local oceanic conditions.

Variability in prey field structure drives inter-annual differences in prey encounter by a marine predator, the little penguin.

Understanding how marine predators encounter prey across patchy landscapes remains challenging due to difficulties in measuring the three-dimensional structure of pelagic prey fields at scales relevant to animal movement. We measured at-sea behaviour of a central-place forager, the little penguin (Eudyptula minor), over 5 years (2015–2019) using GPS and dive loggers. We made contemporaneous measurements of the prey field within the penguins' foraging range via boat-based acoustic surveys. We developed a prey encounter index by comparing estimates of acoustic prey density encountered along actual penguin tracks to those encountered along simulated penguin tracks with the same characteristics as real tracks but that moved randomly through the prey field. In most years, penguin tracks encountered prey better than simulated random movements greater than 99% of the time, and penguin dive depths matched peaks in the vertical distribution of prey. However, when prey was unusually sparse and/or deep, penguins had worse than random prey encounter indices, exhibited dives that mismatched depth of maximum prey density, and females had abnormally low body mass (5.3% lower than average). Reductions in prey encounters owing to decreases in the density or accessibility of prey may ultimately lead to reduced fitness and population declines in central-place foraging marine predators.

A Novel Approach to Using Seabed Geomorphology as a Predictor of Habitat Use in Highly Mobile Marine Predators: Implications for Ecology and Conservation

Understanding how marine predators find patchily distributed prey resources in a dynamic environment is key to identifying important ecological areas for ecosystem-level conservation management. However, the mechanisms underpinning important foraging areas often result from complex interactions between static and dynamic covariates (e.g. topography and currents). Modelling habitat associations with hydrodynamic processes is rarely useful when attempting to identify and characterise foraging areas across an individual’s foraging range. Investigating the influence of static habitat features on predator behaviour can provide a more tractable baseline understanding of habitat associations, upon which additional complexity can be added. Seabed gradient covariates (e.g. slope and aspect) are often used, yet such metrics are computed at singular user-defined resolutions, and provide limited ecological insight when used in isolation. Instead, categorising the seabed into geomorphological features may provide better characterisation of seabed structure. Here we explore the utility of a pattern recognition algorithm to delineate whole geomorphological features (“geomorphons”) on the seabed (e.g. valleys, ridges, footslopes) from bathymetry data, and examine the influence of geomorphology on marine predator habitat use. We demonstrate the potential application of this approach in a case study, examining the influence of geomorphons on the at-sea behaviour of a highly mobile predator inhabiting shelf seas: the grey seal (Halichoerus grypus). We analyse GPS tracking data from three seals tagged in the southern North Sea, an area with heterogeneous geomorphology. We use hidden Markov models (HMMs) to infer foraging and travelling behaviour and model the effect of different feature types on the probability of switching between states. All three seals showed an increased probability of transitioning from travelling to foraging when encountering slopes, footslopes and hollows, and foraging activity was concentrated at slopes on the fringes of the Dogger Bank. We hypothesise that such features may host prey aggregations, and/or lead to increased prey capture success. The results suggest the importance of such areas for grey seals in the southern North Sea, a region undergoing rapid and widespread anthropogenic habitat change. This method could be incorporated into future species distribution models to improve estimates of predator distribution, informing conservation management and marine spatial planning.

Deep inference of seabird dives from GPS-only records: Performance and generalization properties.

At-sea behaviour of seabirds have received significant attention in ecology over the last decades as it is a key process in the ecology and fate of these populations. It is also, through the position of top predator that these species often occupy, a relevant and integrative indicator of the dynamics of the marine ecosystems they rely on. Seabird trajectories are recorded through the deployment of GPS, and a variety of statistical approaches have been tested to infer probable behaviours from these location data. Recently, deep learning tools have shown promising results for the segmentation and classification of animal behaviour from trajectory data. Yet, these approaches have not been widely used and investigation is still needed to identify optimal network architecture and to demonstrate their generalization properties. From a database of about 300 foraging trajectories derived from GPS data deployed simultaneously with pressure sensors for the identification of dives, this work has benchmarked deep neural network architectures trained in a supervised manner for the prediction of dives from trajectory data. It first confirms that deep learning allows better dive prediction than usual methods such as Hidden Markov Models. It also demonstrates the generalization properties of the trained networks for inferring dives distribution for seabirds from other colonies and ecosystems. In particular, convolutional networks trained on Peruvian boobies from a specific colony show great ability to predict dives of boobies from other colonies and from distinct ecosystems. We further investigate accross-species generalization using a transfer learning strategy known as 'fine-tuning'. Starting from a convolutional network pre-trained on Guanay cormorant data reduced by two the size of the dataset needed to accurately predict dives in a tropical booby from Brazil. We believe that the networks trained in this study will provide relevant starting point for future fine-tuning works for seabird trajectory segmentation.

How shearwaters prey. New insights in foraging behaviour and marine foraging associations using bird-borne video cameras

Conventional bio-logging techniques used for ethological studies of seabirds have their limitations when studying detailed behaviours at sea. This study uses animal-borne video cameras to reveal fine-scale behaviours, associations with conspecifics and other species and interactions with fishery vessels during foraging of a Mediterranean seabird. The study was conducted on Scopoli's shearwaters (Calonectris diomedea) breeding in Linosa island (35°51′33″ N; 12°51′34″ E) during summer 2020. Foraging events were video recorded from a seabirds' view with lightweight cameras attached to the birds' back. Foraging always occurred in association with other shearwaters. Competitive events between shearwaters were observed, and their frequency was positively correlated to the number of birds in the foraging aggregation. Associations with tunas and sea turtles have been frequent observations at natural foraging sites. During foraging events, video recordings allowed observations of fine-scale behaviours, which would have remained unnoticed with conventional tracking devices. Foraging events could be categorised by prey type into “natural prey” and “fishery discards”. Analysis of the video footage suggests behavioural differences between the two prey type categories. Those differences suggest that the foraging effort between natural prey and fishery discards consumption can vary, which adds new arguments to the discussion about energy trade-offs and choice of foraging strategy. These observations highlight the importance of combining tracking technologies to obtain a complete picture of the at-sea behaviours of seabirds, which is essential for understanding the impact of foraging strategies and seabird-fishery interactions.Graphical abstract

Video and acceleration records of streaked shearwaters allows detection of two foraging behaviours associated with large marine predators.

The study of seabird behaviour has largely relied on animal-borne tags to gather information, requiring interpretation to estimate at-sea behaviours. Details of shallow-diving birds’ foraging are less known than deep-diving species due to difficulty in identifying shallow dives from biologging devices. Development of smaller video loggers allow a direct view of these birds’ behaviours, at the cost of short battery capacity. However, recordings from video loggers combined with relatively low power usage accelerometers give a means to develop a reliable foraging detection method. Combined video and acceleration loggers were attached to streaked shearwaters in Funakoshi-Ohshima Island (39°24’N,141°59’E) during the breeding season in 2018. Video recordings were classified into behavioural categories (rest, transit, and foraging) and a detection method was generated from the acceleration signals. Two foraging behaviours, surface seizing and foraging dives, are reported with video recordings. Surface seizing was comprised of successive take-offs and landings (mean duration 0.6 and 1.5s, respectively), while foraging dives were shallow subsurface dives (3.2s mean duration) from the air and water surface. Birds were observed foraging close to marine predators, including dolphins and large fish. Results of the behaviour detection method were validated against video recordings, with mean true and false positive rates of 90% and 0%, 79% and 5%, and 66% and <1%, for flight, surface seizing, and foraging dives, respectively. The detection method was applied to longer duration acceleration and GPS datasets collected during the 2018 and 2019 breeding seasons. Foraging trips lasted between 1 − 8 days, with birds performing on average 16 surface seizing events and 43 foraging dives per day, comprising <1% of daily activity, while transit and rest took up 55 and 40%, respectively. This foraging detection method can address the difficulties of recording shallow-diving foraging behaviour and provides a means to measure activity budgets across shallow diving seabird species.

Similar at-sea behaviour but different habitat use between failed and successful breeding albatrosses

Breeding failure is expected to induce behavioural changes in central place foragers. Indeed, after a failed reproductive attempt, breeding individuals are relieved from having to return to their breeding site for reproductive duties and thus are less constrained than successful breeders in their movements during the remainder of the breeding season. Accordingly, they are expected to adjust their behaviour, travelling longer in distance and/or time to reach foraging grounds. They are also expected to use different foraging areas to decrease local intra-specific competition with successful breeders. We compared the at-sea behaviour and habitat use of successful and failed Indian yellow-nosed albatrosses nesting in Amsterdam Island, Southern Indian Ocean, during 2 chick-rearing seasons. Failed breeders exhibited the same at-sea foraging behaviour, travelling as far and as long as successful breeders. They also spent the same amount of time on their nest between at-sea trips. Nevertheless, habitat models revealed partial spatial segregation of failed breeders, which used specific foraging areas characterized by deeper and colder waters in addition to the areas they shared with successful breeders. Our study shows the importance of combining a range of analytical methods (spatial analysis, behavioural inferences with advanced movement models and habitat models) to infer the at-sea behaviour and habitat use of seabirds. It also stresses the importance of considering individual breeding status when aiming to understand the spatial distribution of individuals, especially when this information may have conservation implications.

Foraging niche overlap during chick-rearing in the sexually dimorphic Westland petrel.

Most Procellariform seabirds are pelagic, breed in summer when prey availability peaks, and migrate for winter. They also display a dual foraging strategy (short and long trips) and sex-specific foraging. The Westland petrel Procellaria westlandica, a New Zealand endemic, is one of the rare seabirds breeding in winter. Preliminary findings on this large and sexually dimorphic petrel suggest a foraging behaviour with no evidence of a dual strategy, within a narrow range and with shared areas between sexes. To investigate further this unusual strategy, the present study determined the fine-scale at-sea behaviours (global positioning system and accelerometer data loggers) and trophic niches (stable isotopes in whole blood) of chick-rearing individuals (16 males and 13 females). All individuals foraged on the shelf-slope of the west coast of New Zealand's South Island with short, unimodal trips. Both sexes foraged at similar intensity without temporal, spatial or isotopic niche segregation. These findings suggest the presence of a winter prey resource close to the colony, sufficient to satisfy the nutritional needs of breeding without increasing the foraging effort or intra-specific competition avoidance during winter. Additional data are needed to assess the consistency of foraging niche between the sexes and its reproductive outcomes in view of anticipated environmental changes.

Short-term behavioural impact contrasts with long-term fitness consequences of biologging in a long-lived seabird

Biologging has emerged as one of the most powerful and widely used technologies in ethology and ecology, providing unprecedented insight into animal behaviour. However, attaching loggers to animals may alter their behaviour, leading to the collection of data that fails to represent natural activity accurately. This is of particular concern in free-ranging animals, where tagged individuals can rarely be monitored directly. One of the most commonly reported measures of impact is breeding success, but this ignores potential short-term alterations to individual behaviour. When collecting ecological or behavioural data, such changes can have important consequences for the inference of results. Here, we take a multifaceted approach to investigate whether tagging leads to short-term behavioural changes, and whether these are later reflected in breeding performance, in a pelagic seabird. We analyse a long-term dataset of tracking data from Manx shearwaters (Puffinus puffinus), comparing the effects of carrying no device, small geolocator (GLS) devices (0.6% body mass), large Global Positioning System (GPS) devices (4.2% body mass) and a combination of the two (4.8% body mass). Despite exhibiting normal breeding success in both the year of tagging and the following year, incubating birds carrying GPS devices altered their foraging behaviour compared to untagged birds. During their foraging trips, GPS-tagged birds doubled their time away from the nest, experienced reduced foraging gains (64% reduction in mass gained per day) and reduced flight time by 14%. These findings demonstrate that the perceived impacts of device deployment depends on the scale over which they are sought: long-term measures, such as breeding success, can obscure finer-scale behavioural change, potentially limiting the validity of using GPS to infer at-sea behaviour when answering behavioural or ecological questions.

Predicting the exposure of diving grey seals to shipping noise

There is high spatial overlap between grey seals and shipping traffic, and the functional hearing range of grey seals indicates sensitivity to underwater noise emitted by ships. However, there is still very little data regarding the exposure of grey seals to shipping noise, constraining effective policy decisions. Particularly, there are few predictions that consider the at-sea movement of seals. Consequently, this study aimed to predict the exposure of adult grey seals and pups to shipping noise along a three-dimensional movement track, and assess the influence of shipping characteristics on sound exposure levels. Using ship location data, a ship source model, and the acoustic propagation model, RAMSurf, this study estimated weighted 24-h sound exposure levels (10-1000 Hz) (SELw). Median predicted 24-h SELw was 128 and 142 dB re 1 μPa2s for the pups and adults, respectively. The predicted exposure of seals to shipping noise did not exceed best evidence thresholds for temporary threshold shift. Exposure was mediated by the number of ships, ship source level, the distance between seals and ships, and the at-sea behaviour of the seals. The results can inform regulatory planning related to anthropogenic pressures on seal populations.

Daily and seasonal movements of Cape Cod gray seals vary with predation risk

White sharks Carcharodon carcharias and gray seals Halichoerus grypus are re-establishing their ecological roles within the Northwestern Atlantic Ocean, presenting an opportunity to understand gray seal movement and at-sea behavior under predation risk. As with other shark-seal hotspots, movements to and from terrestrial haul outs can be risky for gray seals, thereby eliciting antipredator strategies. We investigated the movement and coastal behavior of gray seals on Cape Cod (USA) in relation to seasonal and diel changes in white shark activity. Analyzing 412 trips to sea by 8 seals and more than 25000 acoustic detections from 23 individual white sharks, we observed seasonally homogeneous movements in seal behavior during months with greater shark presence. During riskier months, seal behavior manifested in near-exclusive nocturnal foraging, reduced offshore ranging, and limited at-sea activity. On these nocturnal trips to sea, seals returning to haul outs tended to avoid daybreak and traversed during diel minima in shark activity. However, seals tended to depart haul outs at dusk when shark presence was maximal. As conservation efforts succeed in rebuilding depleted populations of coastal predators, studying re-emerging predator-prey interactions can enhance our understanding about the drivers of movement and behavior.

Spatial ecology of closely related taxa: the case of the little shearwater complex in the North Atlantic Ocean

Abstract Seabirds inhabiting vast water masses provide numerous examples where opposing phenomena, such as natal and breeding philopatry vs. vagility have dug cryptic taxonomic boundaries among closely related taxa. The taxonomy of little shearwaters of the North Atlantic Ocean (Little–Audubon’s shearwater complex, Puffinus assimilis–lherminieri) still remains unclear, and complementary information on non-breeding distributions and at-sea behaviour becomes essential to unravel divergent local adaptations to specific habitats. Using miniaturized light-level geolocators from seven study areas in the North Atlantic, we evaluate the spatial and habitat segregation, estimate the timing of their key life-cycle events and describe the at-sea behaviour of three taxa of these little shearwaters year-round to distinguish ecological patterns and specializations that could ultimately unravel potential lineage divergences. We also assess morphometric data from birds that were breeding at each study area to further discuss potential adaptations to specific habitats. Our results show that, while birds from different taxa segregated in space and habitats, they share ecological plasticity, similar annual phenology and diel foraging behaviour. These ecological inconsistencies, while defining the evolutionary stressors faced by these taxa, do not suggest the existence of three Evolutionary Significant Units. However, they confirm the recent evolutionary divergence among the three little shearwaters of the North Atlantic.

Spatial ecology, phenological variability and moulting patterns of the Endangered Atlantic petrel Pterodroma incerta

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 40:189-206 (2019) - DOI: https://doi.org/10.3354/esr00991 ESR Special: Biologging in conservation Spatial ecology, phenological variability and moulting patterns of the Endangered Atlantic petrel Pterodroma incerta Marina Pastor-Prieto1,*, Raül Ramos1, Zuzana Zajková1,2, José Manuel Reyes-González1, Manuel L. Rivas1, Peter G. Ryan3, Jacob González-Solís1 1Institut de Recerca de la Biodiversitat (IRBio) and Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals (BEECA), Universitat de Barcelona, 08028 Barcelona, Spain 2Center for Advanced Studies of Blanes (CEAB-CSIC), 17300 Girona, Spain 3FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, South Africa *Corresponding author: marina.pastor6@gmail.com ABSTRACT: Insights into the year-round movements and behaviour of seabirds are essential to better understand their ecology and to evaluate possible threats at sea. The Atlantic petrel Pterodroma incerta is an Endangered gadfly petrel endemic to the South Atlantic Ocean, with virtually the entire population breeding on Gough Island (Tristan da Cunha archipelago). We describe adult phenology, habitat preferences and at-sea activity patterns for each phenological phase of the annual cycle and refine current knowledge about its distribution, by using light-level geolocators on 13 adults over 1-3 consecutive years. We also ascertained moulting pattern through stable isotope analysis (SIA) of nitrogen and carbon in feathers from 8 carcasses. On average, adults started their post-breeding migration on 25 December, taking 10 d to reach their non-breeding areas on the South American shelf slope. The pre-breeding migration started around 11 April and took 5 d. From phenological data, we found evidence of carry-over effects between successive breeding periods. The year-round distribution generally coincided with the potential distribution obtained from habitat modelling, except during the non-breeding and pre-laying exodus periods, when birds only used the western areas of the South Atlantic. Moulting occurred during the non-breeding period, when birds spent more time on the water, and results from SIA helped us to distinguish feathers grown around Gough Island from those grown in the non-breeding area. Overall, our results bring important new insights into the spatial ecology of this Endangered seabird, which should help improve conservation strategies in the South Atlantic Ocean. KEY WORDS: Atlantic petrel · Year-round movements · At-sea behaviour · Carry-over effects · Patagonian Shelf Full text in pdf format Supplementary material PreviousNextCite this article as: Pastor-Prieto M, Ramos R, Zajková Z, Reyes-González JM, Rivas ML, Ryan PG, González-Solís J (2019) Spatial ecology, phenological variability and moulting patterns of the Endangered Atlantic petrel Pterodroma incerta. Endang Species Res 40:189-206. https://doi.org/10.3354/esr00991 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 40. Online publication date: November 14, 2019 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2019 Inter-Research.

Patterns of at-sea behaviour at a hybrid zone between two threatened seabirds

Patterns of behavioural variation and migratory connectivity are important characteristics of populations, particularly at the edges of species distributions, where processes involved in influencing evolutionary trajectories, such as divergence, mutual persistence, and natural hybridization, can occur. Here, we focused on two closely related seabird species that breed in the Mediterranean: Balearic shearwaters (Puffinus mauretanicus) and Yelkouan shearwaters (Puffinus yelkouan). Genetic and phenotypic evidence of hybridization between the two species on Menorca (the eastern and westernmost island in the breeding ranges of the two shearwaters, respectively) has provided important insights into relationships between these recently diverged species. Nevertheless, levels of behavioural and ecological differentiation amongst these populations remain largely unknown. Using geolocation and stable isotopes, we compared the at-sea movement behaviour of birds from the Menorcan ‘hybrid’ population with the nearest neighbouring populations of Balearic and Yelkouan shearwaters. The Menorcan population displayed a suite of behavioural features intermediate to those seen in the two species (including migration strategies, breeding season movements and limited data on phenology). Our findings provide new evidence to support suggestions that the Menorcan population is admixed, and indicate a role of non-breeding behaviours in the evolutionary trajectories of Puffinus shearwaters in the Mediterranean.

Improving emergence location estimates for Argos pop-up transmitters

BackgroundRecent advances in satellite tagging technologies for marine animals have provided opportunities to investigate the spatial ecology of pelagic species including at-sea behavior and predator–prey interactions. Implantable Life History Transmitters (LHX tags) provide postmortem data on location and causes of mortalities from tagged individuals. Following a mortality event and extrusion of the tag from within an animal, varying amounts of time may elapse between the onset of satellite transmissions, the first successful uplinks to the Argos satellite system and the first location estimate obtained from multiple uplinks. Externally attached pop-up archival transmitters (PAT tags) also only commence transmissions following pre-programmed detachment from a host. The amount of delay for both types of tags may vary with programming, sea state (e.g., wind, waves, currents and tides) tag exposure and satellite coverage. Thus, actual emergence locations for LHX and other pop-up satellite transmitters are hard to accurately determine. Larger errors (~ 10–50 km) may be associated with emergence locations than the errors inherent in the Argos system. Here we present a new approach based on a time-reversed state-space model to improving emergence location estimates and quantifying their uncertainty for pop-up satellite transmitters, using data from 24 LHX tags deployed at known locations in the Gulf of Alaska.ResultsBetween May and June 2017, we deployed 12 LHX tags in two locations in Resurrection Bay and 12 tags in two locations in Prince William Sound, Alaska. When tracking models included all successful uplinks that resulted in Argos locations immediately after deployments, the emergence location could be predicted to within 3 km, on average. However, increasing transmission delays up to 16 h progressively reduced the accuracy to 6–12 km, and for delays of 24 h or longer, the actual emergence locations were outside of the 95% isopleth of estimates.ConclusionsEmergence locations for pop-up satellite transmitters can be estimated by a time-reversed state-space model. The area confined by 95% isopleth of model output is an effective way to characterize an emergence location with an associated uncertainty. Our findings illustrate the importance of programming tags to enhance satellite uplinks to provide immediate and high-quality locations.

A sex-influenced flexible foraging strategy in a tropical seabird, the magnificent frigatebird

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 611:203-214 (2019) - DOI: https://doi.org/10.3354/meps12859 A sex-influenced flexible foraging strategy in a tropical seabird, the magnificent frigatebird Rhiannon E. Austin1,2,*,**, Federico De Pascalis1, John P. Y. Arnould3, Jane Haakonsson4, Stephen C. Votier2, Gina Ebanks-Petrie4, Tim Austin4, Greg Morgan5, Georgia Bennett1, Jonathan A. Green1 1School of Environmental Sciences, University of Liverpool, Liverpool L69 3GP, UK 2Environment and Sustainability Institute, University of Exeter, Penryn TR10 9FE, UK 3School of Life and Environmental Sciences, Burwood Campus, Deakin University, Burwood, VIC 3125, Australia 4Department of Environment, Cayman Islands Government, Grand Cayman, KY1-1002, Cayman Islands 5RSPB, Ramsey Island, St Davids, Pembrokeshire SA62 6PY, UK *Corresponding author: rhiannoneaustin@gmail.com**née Meier ABSTRACT: To successfully exploit resources, animals must be adapted to operate under phenotypic and environmental constraints. The strategies that predators use to locate prey are therefore diverse, particularly for breeding central-place foragers that must balance investment in reproduction and self-maintenance. Magnificent frigatebirds Fregata magnificens are tropical seabirds with intriguing morphology and feeding ecology, which display strikingly unequal levels of parental care (males deserting offspring months before females). These unusual traits can better help us understand the links between movement behaviour and breeding strategies in this poorly studied species. Using archival GPS, GPS-GSM loggers, bird-borne cameras and dietary data, we investigated the foraging ecology of chick-rearing magnificent frigatebirds from a breeding population in the Cayman Islands. This population engages in 2 main foraging strategies: (1) coastal trips over the continental shelf, where individuals target reef species and engage in kleptoparasitism, and (2) offshore trips during which birds feed on schooling pelagic prey. Differences in strategy use were partially linked to sex, with males (which invest less in offspring) roaming further from nests, and showing a higher propensity to forage offshore. Video data further indicated differences in social information use between strategies: foraging with conspecifics was more prevalent in coastal environments than pelagic. We suggest that observed variation in at-sea behaviour may partially be mediated by sex-based differences in parental roles, and/or size differences leading to intraspecific competition. Our study provides evidence of bimodal foraging and sheds new light on the importance of both pelagic and coastal feeding in this enigmatic species. KEY WORDS: Fregata magnificens · Tracking · Seabird · Feeding ecology · Video logger Full text in pdf format Supplementary material PreviousNextCite this article as: Austin RE, De Pascalis F, Arnould JPY, Haakonsson J and others (2019) A sex-influenced flexible foraging strategy in a tropical seabird, the magnificent frigatebird. Mar Ecol Prog Ser 611:203-214. https://doi.org/10.3354/meps12859 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 611. Online publication date: February 14, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

Comparative foraging and diving behaviour of coexisting breeding and non-breeding King Penguins (Aptenodytes patagonicus) in Tierra del Fuego, Chile

ABSTRACTBreeding status directly affects the at-sea behaviour of seabirds, resulting in marked differences between breeding and non-breeding birds. In this study, we report for the first time the foraging and diving behaviour of coexisting incubating, courting and non-breeding King Penguins (Aptenodytes patagonicus) at a recently established colony in Tierra del Fuego, Chile, to determine differences in (1) the number and duration of the foraging trips, (2) time spent at sea and on land, and (3) diving performance and foraging success. We obtained data from four incubating, five courting and three non-breeding penguins equipped with time–depth recorders during November and December 2014. Incubating birds performed a single but long trip (8.1 ± 1.9 days), while courting birds performed one or two trips of intermediate duration (2.3 ± 0.8 days) and non-breeders made multiple short trips (0.6 ± 0.1 days). Courting birds spent a significantly greater proportion of their time on land than the other birds. Incubating birds performed the deepest and longest dives and had the highest diving efficiency, while non-breeders performed the shallowest and shortest dives and exhibited low diving efficiencies, suggesting that birds are utilising different foraging areas. These results indicate that incubating, courting and non-breeding King Penguins, although coexisting temporally at the same colony, differentially adjust their foraging and diving behaviour, most likely to accomplish their specific social and energetic demands.