A model to estimate seabird field metabolic rates

Island restoration to rebuild seabird populations and amplify coral reef functioning

Mobile organisms like seabirds can provide important nutrient flows between ecosystems, but this connectivity has been interrupted by the degradation of island ecosystems. Island restoration (via invasive species eradications and the restoration of native vegetation) can reestablish seabird populations and their nutrient transfers between their foraging areas, breeding colonies, and adjacent nearshore habitats. Its diverse benefits are making island restoration increasingly common and scalable to larger islands and whole archipelagos. We identified the factors that influence breeding seabird abundances throughout the Chagos Archipelago in the Indian Ocean and conducted predictive modeling to estimate the abundances of seabirds that the archipelago could support under invasive predator eradication and native vegetation restoration scenarios. We explored whether the prey base exists to support restored seabird populations across the archipelago, calculated the nitrogen that restored populations of seabirds might produce via their guano, and modeled the cascading conservation gains that island restoration could provide. Restoration was predicted to increase breeding pairs of seabirds to over 280,000, and prey was predicted to be ample to support the revived seabird populations. Restored nutrient fluxes were predicted to result in increases in coral growth rates, reef fish biomasses, and parrotfish grazing and bioerosion rates. Given these potential cross-ecosystem benefits, our results support island restoration as a conservation priority that could enhance resilience to climatic change effects, such as sea-level rise and coral bleaching. We encourage the incorporation of our estimates of cross-ecosystem benefits in prioritization exercises for island restoration.

A framework to unlock marine bird energetics

Energetics can provide novel insights into the roles of animals, but employing an energetics approach has traditionally required extensive empirical physiological data on the focal species, something that can be challenging for those that inhabit marine environments. There is therefore a demand for a framework through which to estimate energy expenditure from readily available data. We present the energetic costs associated with important time- and energy-intensive behaviours across nine families of marine bird (including seabirds, ducks, divers and grebes) and nine ecological guilds. We demonstrate a worked example, calculating the year-round energetic expenditure of the great auk, Pinguinus impennis, under three migration scenarios, thereby illustrating the capacity of this approach to make predictions for data-deficient species. We provide a comprehensive framework through which to model marine bird energetics and demonstrate the power of this approach to provide novel, quantitative insights into the influence of marine birds within their ecosystems.

The role of seabird guano in maintaining North Atlantic summertime productivity

Nutrients supplied via seabird guano increase primary production in some coastal ecosystems. A similar process may occur in the open ocean. To investigate this directly, we first measured bulk and leachable nutrient concentrations in guano sampled in the North Atlantic. We found that guano was strongly enriched in phosphorus, which was released as phosphate in solution. Nitrogen release was dominated by reduced forms (ammonium and urea) whilst release of nitrate was relatively low. A range of trace elements, including the micronutrient iron, were released. Using in-situ bioassays, we then showed that supply of fresh guano to ambient seawater increases phytoplankton biomass and photochemical efficiencies. Based on these results, modelled seabird distributions, and known defecation rates, we estimate that on annual scales guano is a minor source of nutrients for the surface North Atlantic. However, on shorter timescales in late spring/summer it could be much more important: Estimates of upper-level depositions of phosphorus by seabirds were three orders of magnitude higher than modelled aerosol deposition and comparable to diffusion from deeper waters.

Energetic and behavioral consequences of migration: an empirical evaluation in the context of the full annual cycle

Seasonal migrations are used by diverse animal taxa, yet the costs and benefits of migrating have rarely been empirically examined. The aim of this study was to determine how migration influences two ecological currencies, energy expenditure and time allocated towards different behaviors, in a full annual cycle context. We compare these currencies among lesser black-backed gulls that range from short- (< 250 km) to long-distance (> 4500 km) migrants. Daily time-activity budgets were reconstructed from tri-axial acceleration and GPS, which, in conjunction with a bioenergetics model to estimate thermoregulatory costs, enabled us to estimate daily energy expenditure throughout the year. We found that migration strategy had no effect on annual energy expenditure, however, energy expenditure through time deviated more from the annual average as migration distance increased. Patterns in time-activity budgets were similar across strategies, suggesting migration strategy does not limit behavioral adjustments required for other annual cycle stages (breeding, molt, wintering). Variation among individuals using the same strategy was high, suggesting that daily behavioral decisions (e.g. foraging strategy) contribute more towards energy expenditure than an individual's migration strategy. These findings provide unprecedented new understanding regarding the relative importance of fine versus broad-scale behavioral strategies towards annual energy expenditures.

A bioenergetics approach to understanding sex differences in the foraging behaviour of a sexually monomorphic species

Many animals show sexually divergent foraging behaviours reflecting different physiological constraints or energetic needs. We used a bioenergetics approach to examine sex differences in foraging behaviour of the sexually monomorphic northern gannet. We derived a relationship between dynamic body acceleration and energy expenditure to quantify the energetic cost of prey capture attempts (plunge dives). Fourteen gannets were tracked using GPS, time depth recorders (TDR) and accelerometers. All plunge dives in a foraging trip represented less than 4% of total energy expenditure, with no significant sex differences in expenditure. Despite females undertaking significantly more dives than males, this low energetic cost resulted in no sex differences in overall energy expenditure across a foraging trip. Bayesian stable isotope mixing models based on blood samples highlighted sex differences in diet; however, calorific intake from successful prey capture was estimated to be similar between sexes. Females experienced 10.28% higher energy demands, primarily due to unequal chick provisioning. Estimates show a minimum of 19% of dives have to be successful for females to meet their daily energy requirements, and 26% for males. Our analyses suggest northern gannets show sex differences in foraging behaviour primarily related to dive rate and success rather than the energetic cost of foraging or energetic content of prey.

Untangling local and remote influences in two major petrel habitats in the oligotrophic Southern Ocean

Ocean circulation connects geographically distinct ecosystems across a wide range of spatial and temporal scales via exchanges of physical and biogeochemical properties. Remote oceanographic processes can be especially important for ecosystems in the Southern Ocean, where the Antarctic Circumpolar Current transports properties across ocean basins through both advection and mixing. Recent tracking studies have indicated the existence of two large-scale, open ocean habitats in the Southern Ocean used by grey petrels (Procellaria cinerea) from two populations (i.e., Kerguelen and Antipodes islands) during their nonbreeding season for extended periods during austral summer (i.e., October to February). In this work, we use a novel combination of large-scale oceanographic observations, surface drifter data, satellite-derived primary productivity, numerical adjoint sensitivity experiments, and output from a biogeochemical state estimate to examine local and remote influences on these grey petrel habitats. Our aim is to understand the oceanographic features that control these isolated foraging areas and to evaluate their ecological value as oligotrophic open ocean habitats. We estimate the minimum local primary productivity required to support these populations to be much <1% of the estimated local primary productivity. The region in the southeast Indian Ocean used by the birds from Kerguelen is connected by circulation to the productive Kerguelen shelf. In contrast, the region in the south-central Pacific Ocean used by seabirds from the Antipodes is relatively isolated suggesting it is more influenced by local factors or the cumulative effects of many seasonal cycles. This work exemplifies the potential use of predator distributions and oceanographic data to highlight areas of the open ocean that may be more dynamic and productive than previously thought. Our results highlight the need to consider advective connections between ecosystems in the Southern Ocean and to re-evaluate the ecological relevance of oligotrophic Southern Ocean regions from a conservation perspective.

Preferred reporting items for systematic reviews and meta-analyses in ecology and evolutionary biology: a PRISMA extension

Since the early 1990s, ecologists and evolutionary biologists have aggregated primary research using meta-analytic methods to understand ecological and evolutionary phenomena. Meta-analyses can resolve long-standing disputes, dispel spurious claims, and generate new research questions. At their worst, however, meta-analysis publications are wolves in sheep's clothing: subjective with biased conclusions, hidden under coats of objective authority. Conclusions can be rendered unreliable by inappropriate statistical methods, problems with the methods used to select primary research, or problems within the primary research itself. Because of these risks, meta-analyses are increasingly conducted as part of systematic reviews, which use structured, transparent, and reproducible methods to collate and summarise evidence. For readers to determine whether the conclusions from a systematic review or meta-analysis should be trusted - and to be able to build upon the review - authors need to report what they did, why they did it, and what they found. Complete, transparent, and reproducible reporting is measured by 'reporting quality'. To assess perceptions and standards of reporting quality of systematic reviews and meta-analyses published in ecology and evolutionary biology, we surveyed 208 researchers with relevant experience (as authors, reviewers, or editors), and conducted detailed evaluations of 102 systematic review and meta-analysis papers published between 2010 and 2019. Reporting quality was far below optimal and approximately normally distributed. Measured reporting quality was lower than what the community perceived, particularly for the systematic review methods required to measure trustworthiness. The minority of assessed papers that referenced a guideline (~16%) showed substantially higher reporting quality than average, and surveyed researchers showed interest in using a reporting guideline to improve reporting quality. The leading guideline for improving reporting quality of systematic reviews is the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) statement. Here we unveil an extension of PRISMA to serve the meta-analysis community in ecology and evolutionary biology: PRISMA-EcoEvo (version 1.0). PRISMA-EcoEvo is a checklist of 27 main items that, when applicable, should be reported in systematic review and meta-analysis publications summarising primary research in ecology and evolutionary biology. In this explanation and elaboration document, we provide guidance for authors, reviewers, and editors, with explanations for each item on the checklist, including supplementary examples from published papers. Authors can consult this PRISMA-EcoEvo guideline both in the planning and writing stages of a systematic review and meta-analysis, to increase reporting quality of submitted manuscripts. Reviewers and editors can use the checklist to assess reporting quality in the manuscripts they review. Overall, PRISMA-EcoEvo is a resource for the ecology and evolutionary biology community to facilitate transparent and comprehensively reported systematic reviews and meta-analyses.

Be different to be better: the effect of personality on optimal foraging with incomplete knowledge

Many animal populations include a diversity of personalities, and these personalities are often linked to foraging strategy. However, it is not always clear why populations should evolve to have this diversity. Indeed, optimal foraging theory typically seeks out a single optimal strategy for individuals in a population. So why do we, in fact, see a variety of strategies existing in a single population? Here, we aim to provide insight into this conundrum by modelling the particular case of foraging seabirds, that forage on patchy prey. These seabirds have only partial knowledge of their environment: they do not know exactly where the next patch will emerge, but they may have some understanding of which locations are more likely to lead to patch emergence than others. Many existing optimal foraging studies assume either complete knowledge (e.g. Marginal Value Theorem) or no knowledge (e.g. Lévy Flight Hypothesis), but here we construct a new modelling approach which incorporates partial knowledge. In our model, different foraging strategies are favoured by different birds along the bold-shy personality continuum, so we can assess the optimality of a personality type. We show that it is optimal to be shy (resp. bold) when living in a population of bold (resp. shy) birds. This observation gives a plausible mechanism behind the emergence of diverse personalities. We also show that environmental degradation is likely to favour shyer birds and cause a decrease in diversity of personality over time.

Field and laboratory metabolism and thermoregulation in rhinoceros auklets

Seabirds spend most of their lives at sea, except when visiting their breeding sites. Since the thermal conductivity of water is 25 times higher than that of air, seabirds resting on water lose heat and expend a considerable amount of energy for thermoregulation. For example, rhinoceros auklet (Cerorhinca monocerata), a medium-sized (480620 g) alcid, spends most of its time floating on the sea. In order to estimate the cost of this behavior in terms of their daily energy expenditure (DEE), we studied rhinoceros auklets breeding on Teuri Island, Hokkaido Japan. We measured their resting metabolic rate (RMR) in air and on water by respirometry, and estimated their DEE by the doubly labeled water method. While RMR on water did not vary significantly between 10C and 15C, it was significantly higher at 5C. Air temperature (5.020.0C) had no effect on RMR. The DEE of free-ranging auklets averaged 1,005.5kJday¹ (130.2, n=3). Our results indicate that RMRs are elevated for auklets resting on water, particularly below their lower critical temperature (LCT), compared with in air. Accordingly, spending time above their LCT on water at any time of year will provide enhanced benefits, particularly to seabirds such as rhinoceros auklets which rest a considerable amount of time on water.

A year in the life of a North Atlantic seabird: behavioural and energetic adjustments during the annual cycle

During their annual cycles, animals face a series of energetic challenges as they prioritise different life history events by engaging in temporally and potentially spatially segregated reproductive and non-breeding periods. Investigating behaviour and energy use across these periods is fundamental to understanding how animals survive the changing conditions associated with annual cycles. We estimated year-round activity budgets, energy expenditure, location, colony attendance and foraging behaviour for surviving individuals from a population of common guillemots Uria aalge. Despite the potential constraints of reduced day lengths and sea surface temperatures in winter, guillemots managed their energy expenditure throughout the year. Values were high prior to and during the breeding season, driven by a combination of high thermoregulatory costs, diving activity, colony attendance and associated flight. Guillemots also exhibited partial colony attendance outside the breeding season, likely supported by local resources. Additionally, there was a mismatch in the timing of peaks in dive effort and a peak in nocturnal foraging activity, indicating that guillemots adapted their foraging behaviour to the availability of prey rather than daylight. Our study identifies adaptations in foraging behaviour and flexibility in activity budgets as mechanisms that enable guillemots to manage their energy expenditure and survive the annual cycle.

So far, so good… Similar fitness consequences and overall energetic costs for short and long-distance migrants in a seabird

Although there is a consensus about the evolutionary drivers of animal migration, considerable work is necessary to identify the mechanisms that underlie the great variety of strategies observed in nature. The study of differential migration offers unique opportunities to identify such mechanisms and allows comparisons of the costs and benefits of migration. The purpose of this study was to compare the characteristics of short and long-distance migrations, and fitness consequences, in a long-lived seabird species. We combined demographic monitoring (survival, phenology, hatching success) of 58 Northern Gannets (Morus bassanus) breeding on Bonaventure Island (Canada) and biologging technology (Global Location Sensor or GLS loggers) to estimate activity and energy budgets during the non-breeding period for three different migration strategies: to the Gulf of Mexico (GM), southeast (SE) or northeast (NE) Atlantic coast of the U.S. Survival, timing of arrival at the colony and hatching success are similar for short (NE, SE) and long-distance (GM) migrants. Despite similar fitness consequences, we found, as expected, that the overall energetic cost of migration is higher for long-distance migrants, although the daily cost during migration was similar between strategies. In contrast, daily maintenance and thermoregulation costs were lower for GM migrants in winter, where sea-surface temperature of the GM is 4-7o C warmer than SE and NE. In addition, GM migrants tend to fly 30 min less per day in their wintering area than other migrants. Considering lower foraging effort and lower thermoregulation costs during winter for long-distance migrants, this suggests that the energetic benefits during the winter of foraging in the GM outweigh any negative consequences of the longer-distance migration. These results support the notion that the costs and benefits of short and long-distance migration is broadly equal on an annual basis, i.e. there are no apparent carry-over effects in this long-lived bird species, probably because of the favourable conditions in the furthest wintering area.

A model to estimate seabird field metabolic rates

For free-ranging animals, field metabolic rate (FMR) is the sum of their energy expenditure over a specified period. This quantity is a key component of ecological processes at every biological level. We applied a phylogenetically informed meta-analytical approach to identify the large-scale determinants of FMR in seabirds during the breeding season. Using data from 64 studies of energetics in 47 species, we created a model to estimate FMR for any seabird population. We found that FMR was positively influenced by body mass and colony latitude and that it increased throughout the breeding season from incubation to brood to crèche. FMR was not impacted by colony-relative predation pressure or species average brood size. Based on this model, we present an app through which users can generate estimates of FMR for any population of breeding seabird. We encourage the use of this app to complement behavioural studies and increase understanding of how energetic demands influence the role of seabirds as driving components of marine systems.