sub-Antarctic Environment Research Articles

Birds and mammals assemblages assessment in sub-Antarctic channels of the Kawésqar National Park and Reserve, southern Chile

Clarence Island and its inland channels are part of the Kawésqar National Park and Kawésqar National Reserve, an extensive wilderness area dominated by pristine sub-Antarctic environments and high marine biodiversity. During the summer and winter of 2020, the assemblages of birds and mammals were recorded in 10 sites, and these data, the following aspects were evaluated: 1) the sampling effort used with species accumulation curves and 2) the community structure of the assemblages with alpha and beta diversity. The total richness was 35 species of birds and 6 species of mammals, representing 17% of both groups documented for the sub-Antarctic Ecoregion of Magellan. During summer and winter, low and high values of species richness and abundance were registered, which modulated low and medium values of diversity. The moderate diversity was consistent with the beta diversity values from the Whittaker index, which on average indicates low species replacement in response to seasonal change. By considering that 20 % of the recorded species have high conservation risks, it can be concluded that this type of fauna survey contributes to improve the knowledge and dissemination of the current distribution of these species, and in future scenarios it will be useful to help predict local extinction events for anthropogenic or natural reasons.

High wax ester and triacylglycerol biosynthesis potential in coastal sediments of Antarctic and Subantarctic environments.

The wax ester (WE) and triacylglycerol (TAG) biosynthetic potential of marine microorganisms is poorly understood at the microbial community level. The goal of this work was to uncover the prevalence and diversity of bacteria with the potential to synthesize these neutral lipids in coastal sediments of two high latitude environments, and to characterize the gene clusters related to this process. Homolog sequences of the key enzyme, the wax ester synthase/acyl-CoA:diacylglycerol acyltransferase (WS/DGAT) were retrieved from 13 metagenomes, including subtidal and intertidal sediments of a Subantarctic environment (Ushuaia Bay, Argentina), and subtidal sediments of an Antarctic environment (Potter Cove, Antarctica). The abundance of WS/DGAT homolog sequences in the sediment metagenomes was 1.23 ± 0.42 times the abundance of 12 single-copy genes encoding ribosomal proteins, higher than in seawater (0.13 ± 0.31 times in 338 metagenomes). Homolog sequences were highly diverse, and were assigned to the Pseudomonadota, Actinomycetota, Bacteroidota and Acidobacteriota phyla. The genomic context of WS/DGAT homologs included sequences related to WE and TAG biosynthesis pathways, as well as to other related pathways such as fatty-acid metabolism, suggesting carbon recycling might drive the flux to neutral lipid synthesis. These results indicate the presence of abundant and taxonomically diverse bacterial populations with the potential to synthesize lipid storage compounds in marine sediments, relating this metabolic process to bacterial survival.

Growth rates and ages of some key tree species from subantarctic Auckland and Campbell Islands

Interspecific variation in tree growth rate and maximum age is central to understanding and predicting the dynamics of forest ecosystems. While there are abundant sources of this information for economically important New Zealand timber species and other common tree species, data for trees from subantarctic environments are almost entirely lacking. Here we present measurements of growth from Auckland and Campbell Islands for three species: Metrosideros umbellata (southern rātā; Myrtaceae, n = 1 site), a canopy dominant; Dracophyllum sp.

What is the menu today in a subantarctic kelp food web from the Kerguelen Islands? Phytodetritus, phytoplankton and phytobenthos; not living kelp

Kelp forests dominated by Macrocystis pyrifera are widely distributed in coastal waters from boreal, temperate and subantarctic regions. This widespread distribution may result in regional differences in food web structure and functioning. In temperate northern regions, where most studies on kelp forest benthic food webs have been conducted, kelp grazing is a well-documented phenomenon and can lead to the overgrazing of M. pyrifera by sea urchins when their predators (e.g., sea otters) are absent. In contrast, little is known about their counterparts in subantarctic areas. The present study aimed to reconstruct the benthic food web of a kelp forest dominated by M. pyrifera in a subantarctic environment using stable isotope analysis. Stable carbon (δ13C), nitrogen (δ15N) and sulfur (δ34S) isotope ratios were measured from food sources (macrophytobenthos, suspended particulate organic matter SPOM, and sediment) and consumers (sponges, bivalves, gastropods, sedentary and mobile polychaetes, arthropods and echinoderms) which were sampled in a kelp forest of the Kerguelen archipelago. Mixing models highlighted two interconnected trophic pathways which were either supported by SPOM and resuspended macrophytobenthos detritus (bentho-pelagic), or by live micro/macrophytobenthos (phytobenthos-based). No major prey were highlighted for several consumers, indicating the existence of potential supplementary trophic pathways. No consumer relying primarily on living M. pyrifera was highlighted by the mixing models. The investigated kelp forest is hence a complex ecosystem supporting multiple trophic pathways, and direct consumption of M. pyrifera is limited. Nonetheless, M. pyrifera and other macrophytobenthos species may constitute a pool of detritus supporting several trophic pathways.

Anthropogenic microfibers are highly abundant at the Burdwood Bank seamount, a protected sub-Antarctic environment in the Southwestern Atlantic Ocean

Microplastics debris in the marine environment have been widely studied across the globe. Within these particles, the most abundant and prevalent type in the oceans are anthropogenic microfibers (MFs), although they have been historically overlooked mostly due to methodological constraints. MFs are currently considered omnipresent in natural environments, however, contrary to the Northern Hemisphere, data on their abundance and distribution in Southern Oceans ecosystems are still scarce, in particular for sub-Antarctic regions. Using Niskin bottles we've explored microfibers abundance and distribution in the water column (3–2450 m depth) at the Burdwood Bank (BB), a seamount located at the southern extreme of the Patagonian shelf, in the Southwestern Atlantic Ocean. The MFs detected from filtered water samples were photographed and measured using ImageJ software, to estimate length, width, and the projected surface area of each particle. Our results indicate that small pieces of fibers are widespread in the water column at the BB (mean of 17.4 ± 12.6 MFs.L−1), from which, 10.6 ± 5.3 MFs.L−1 were at the surface (3–10 m depth), 20 ± 9 MFs.L−1 in intermediate waters (41–97 m), 24.6 ± 17.3 MFs.L−1 in deeper waters (102–164 m), and 9.2 ± 5.3 MFs.L−1 within the slope break of the seamount. Approximately 76.1% of the MFs were composed of Polyethylene terephthalate, and the abundance was dominated by the size fraction from 0.1 to 0.3 mm of length. Given the high relative abundance of small and aged MFs, and the oceanographic complexity of the study area, we postulate that MFs are most likely transported to the BB via the Antarctic Circumpolar Current. Our findings imply that this sub-Antarctic protected ecosystem is highly exposed to microplastic pollution, and this threat could be spreading towards the highly productive waters, north of the study area.

Determining the distributions of plant communities in subantarctic vegetation using species distribution models

Context Mapping of vegetation is important in understanding its dynamics in relation to climate change and disturbance. We investigated using species distribution models to predict plant species assemblages in a subantarctic environment where traditional image interpretation methods of vegetation mapping are limited by image availability and ability to discriminate vegetation types. Aims We test the efficacy for mapping of modelling the range and core range of common species. We also determine the relative importance of predictor variables for each of nine species. Methods We used random forest models to predict the total range and core range (>25% projected foliage cover) of nine potentially dominant plant species and determined the contributions of predictor variables to the models for each species. Key results Widespread species with extensively overlapping ranges were spatially more partitioned with modelling based on core range than with presence or absence modelling. The core range input produced a vegetation map that better approximated observed vegetation patterns than that from presence or absence data. The most important predictor variable varied between species, with elevation, distance from coast, latitude and an across island gradient (similar to longitude) being most influential. Conclusions Species distribution models using three categories (absent, <25% cover, ≥25% cover) and topographic variables derived from a digital elevation model can be used to model the distribution of vegetation assemblages in situations where presence or absence species models cannot discriminate assemblages. Implications Readily collected point location species data could be used to investigate change over time in the spatial extent of both species and vegetation types.

Gastrointestinal Microbiota and Parasite-Fauna of Wild Dissostichus eleginoides Smitt, 1898 Captured at the South-Central Coast of Chile.

Dissotichus eleginoides has a discontinuous circumpolar geographic distribution restricted to mountains and platforms, mainly in Subantarctic and Antarctic waters of the southern hemisphere, including the Southeast Pacific, Atlantic and Indian oceans and in areas surrounding the peninsular platforms of subantarctic islands. The aim of this work was to determine and characterize the gastrointestinal parasitic and microbial fauna of specimens of D. eleginoides captured in waters of the south-central zone of Chile. The magnitude of parasitism in D. eleginoides captured in waters of the south-central zone of Chile is variable, and the parasite richness is different from that reported in specimens from subantarctic environments. Next-generation sequencing (NGS) of the microbial community associated to intestine showed a high diversity, where Proteobacteria, Firmicutes, and Bacteriodetes were the dominant phyla. However, both parasitic and microbial structures can vary between fish from different geographic regions

Marine habitat use and feeding ecology of introduced anadromous brown trout at the colonization front of the sub-Antarctic Kerguelen archipelago

In 1954, brown trout were introduced to the Kerguelen archipelago (49°S, 70°E), a pristine, sub-Antarctic environment previously devoid of native freshwater fishes. Trout began spreading rapidly via coastal waters to colonize adjacent watersheds, however, recent and unexpectedly the spread has slowed. To better understand the ecology of the brown trout here, and why their expansion has slowed, we documented the marine habitat use, foraging ecology, and environmental conditions experienced over one year by 50 acoustically tagged individuals at the colonization front. Trout mainly utilized the marine habitat proximate to their tagging site, ranging no further than 7 km and not entering any uncolonized watersheds. Nutritional indicators showed that trout were in good condition at the time of tagging. Stomach contents and isotope signatures in muscle of additional trout revealed a diet of amphipods (68%), fish (23%), isopods (6%), and zooplankton (6%). The small migration distances observed, presence of suitable habitat, and rich local foraging opportunities suggest that trout can achieve their resource needs close to their home rivers. This may explain why the expansion of brown trout at Kerguelen has slowed.

Anthropogenic Microfibers are Highly Abundant at the Burdwood Bank Seamount, a Protected Sub-Antarctic Environment in the Southwestern Atlantic Ocean

Anthropogenic Microfibers are Highly Abundant at the Burdwood Bank Seamount, a Protected Sub-Antarctic Environment in the Southwestern Atlantic Ocean

Environmental factors regulate occupancy of free-ranging dogs on a sub-Antarctic island, Chile

Domestic dogs (Canis familiaris) are the most common carnivore species in natural ecosystems worldwide. They are of considerable concern for wildlife conservation, particularly in the absence of predators. However, we are only beginning to understand the ecology of free-ranging dogs, and even less is known in sub-Antarctic environments. Here, we used camera-trap data to assess space use of free-ranging dogs on a sub-Antarctic island in the Cape Horn Biosphere Reserve, southern Chile, which lacks native terrestrial carnivores. We predicted free-ranging dogs to be associated with human settlements, trails, and roads and to prefer open habitats over forest for the ease of movement. We obtained 67 independent dog records of 62 individuals over 3909 camera-trap days from 200 sites. Single-species single-season occupancy models revealed that both rural/village dogs, as well as putative feral dogs chose peatbogs over forest, but their preference for settlements and roads was less pronounced and inconsistent among dog categories. Our findings revealed evidence for a reproducing feral dog population on Navarino Island that may be sustained by recruits from rural/village dogs, as identical sites were visited by both dog categories. However, due to a higher occupancy with proximity to human dwellings, the dependence of feral dogs on human resources remain uncontested. In light of the penetration of dogs into pristine sub-Antarctic habitats and their possible impacts on native vulnerable prey, we recommend the implementation of responsible pet-ownership regulations, as well as ethically-approved control actions for feral dogs to protect one of the planet’s last wilderness areas.

Compound‐Specific Radiocarbon Analysis of (Sub‐)Antarctic Coastal Marine Sediments—Potential and Challenges for Chronologies

AbstractIn Antarctic and Subantarctic environments, 14C‐based age determination is often challenging due to unknown reservoir effects, low organic carbon contents of sediments, and high contributions of petrogenic (14C‐free) carbon in ice marginal settings. In this study, we evaluate possible benefits and challenges of compound‐specific radiocarbon analysis (CSRA) as a tool for age determination of marine Antarctic and Subantarctic sediment sequences. We present a comprehensive data set of 14C ages obtained on bulk organic carbon, carbonates, and on fatty acids (FA) from three coastal marine sediment cores from Subantarctic South Georgia and East Antarctica. Low molecular weight (LMW) FA represent the least 14C‐depleted fraction, indicating that the phytoplankton‐derived compounds can be a means of dating sediments. In contrast, vascular plant‐derived high molecular weight FA are systematically depleted in 14C relative to the low molecular weight homologues, reflecting processes such as soil formation/erosion in the catchment. Comparative age‐depth models show significant differences, depending on the material used for the respective models. While the land plant‐derived FA may lead to an overestimation of the actual sediment age, LMW FA reveal complex aquatic reservoir effects. Bulk sedimentary organic carbon 14C ages likely provide appropriate age estimates in settings with low petrogenic carbon input in the Antarctic, whereas CSRA has the potential to produce improved age control in settings with high contributions of petrogenic carbon.

Sharp phylogeographical differentiation near the southern range edge of the silverside Odontesthes nigricans: Distinct peripheral populations and incipient speciation?

The silverside Odontesthes nigricans is the Atheriniform species that reach the southernmost latitude in Patagonia. Its wide distribution ranges from temperate waters in the Atlantic coast of South America (39°S, Buenos Aires Province, Argentina) to the Sub-Antarctic environment of Cape Horn (56°S). A previous study has shown significant intraspecific differences on growth parameters and otolith morphology between the southern peripheral population of O. nigricans in the Beagle Channel and the populations in the Atlantic coast of Tierra del Fuego. In this work, we report the first data on population genetics of O. nigricans along the southern part of its distributional range, including the peripheral populations of Beagle Channel. To examine the genetic variability, we analyzed 224 sequences of 815 bp of mitochondrial control region generated from individuals captured at two sites in the Beagle Channel and six sites at the Atlantic coast. The genetic structure assessment revealed a sharp phylogeographic division between Beagle Channel and the Atlantic coast of Patagonia with a 39.83% of variance among groups. The observed genetic diversity was lower in Beagle Channel than in the Atlantic coast sites and the demographic analyses are compatible with a scenario of past population expansion, especially in Beagle Channel. We hypothesize two possible scenarios: one is a recent colonization of the Beagle Channel from the Atlantic Coast followed by divergence promoted by adaptation to local conditions. On the other hand, population differentiation may have been attained or initiated in allopatric conditions during Quaternary glacial phases and the populations may now be experiencing a secondary contact near the eastern tip of Tierra del Fuego. These hypotheses should be addressed in the future with genomics tools. By now, these populations should be considered as different units for conservation and management purposes.

Harmful phytoplankton in the Beagle Channel (South America) as a potential threat to aquaculture activities

The Beagle Channel is a remote subantarctic environment where mussel aquaculture initiatives have existed since the early 1990s. Here we analyze phytoplankton biomass and composition, and the occurrence of harmful microalgae species and their toxins at three sites during the period 2015–2016. The occurrence of potentially harmful algae was observed throughout the study period, including toxigenic dinoflagellates such as Alexandrium catenella (Group I of the A. tamarense complex), A. ostenfeldii, Dinophysis acuminata, Gonyaulax spinifera, Azadinium sp., and the diatoms Pseudo-nitzschia australis and P. fraudulenta. Toxic dinoflagellates were detected in low densities whereas a Pseudo-nitzschia bloom was observed in late February. Isolates of A. catenella and P. delicatissima sensu stricto were phylogenetically characterized. The toxin profile of A. catenella was dominated by GTX4, while P. delicatissima sensu stricto showed no production of the neurotoxin domoic acid in culture conditions. The results provide base-line information for the management of harmful algal blooms in this little explored subantarctic area.

Correction to: Effects of temperature and salinity on the reproductive phases of Macrocystis pyrifera (L.) C. Agardh (Phaeophyceae) in the Magellan region

The region of Magallanes has the world’s largest sub-Antarctic environments, including the heterogeneous habitats of archipelagos, fjords, channels, and inlets formed by ice advancing and retreating during Quaternary glacial processes. In marine ecosystems, the temperature, salinity, and photoperiod are key parameters which delimit the survival, reproduction and development of the macroalgae and, therefore, the biogeography of numerous sub-Antarctic species. In this research, we compare the reproductive development patterns in spores of Macrocystis pyrifera coming from places with different salinities along longitudinal and latitudinal gradients in Skyring Sound, Otway Sound, the Strait of Magellan (Possession Bay and Puerto del Hambre), and the Beagle Channel (Paula Bay). Laboratory analyses included four salinities and two different temperatures, comparing the percentage of spore germination, sex ratio in females and male gametophytes, and the development of gametogenesis through the proportion of gametophytes and sporophytes, with a factorial experimental design. The best germination percentages were obtained in Puerto del Hambre; the best sex ratio, on the other hand, was in Skyring Sound; finaly, for gametogenesis development, the best results were obtained in Otway Sound and Possession Bay. We prove the temperature and salinity effect over the studied population; moreover, these results demonstrate that at the end of the cycle each population develops more effectively in their local conditions, evidence of a local adaptation in M. pyrifera populations living in contrasting sites in the same region. This is crucial to understand how these populations react to the effect of environmental stressors; furthermore, the selection of appropriate conditions is also an important factor for the future commercial cultivation management of these important macroalgae.

Soil properties on sub-Antarctic Macquarie Island: Fundamental indicators of ecosystem function and potential change

We examined the nature and properties of soils on Australian sub-Antarctic Macquarie Island to determine key environmental factors driving their distribution, development and change. We provide the first classification of these soils using Australian and international (WRB) systems while combining elemental, stable and radio-isotope analysis to interpret processes of soil formation and key controlling environmental factors. Soil organic carbon (SOC) and total nitrogen (TN) concentrations across the island were influenced largely by elevation and topographic position with coastal soils and wetter depressions containing more SOC and TN compared with drier and higher elevation locations. Soils on the high, exposed plateau of the island contained low SOC and TN concentrations by comparison. Results suggested that soils of the coastal zone are subject to ongoing aggradation with significant inputs of nutrient, particularly extractable P (Ext P), from oceanic and especially avifauna sources. Nutrient subsidy was concentrated on coastal margins and the more sheltered eastern side of the island, diminishing significantly with increasing elevation and distance from the coast. Soils of the central plateau contained very low Ext P concentrations throughout the profile and appear to be relic if not degrading. Further comprehensive soil mapping, classification and monitoring across Macquarie Island will elucidate the important role that soils serve for healthy ecosystem function in these sub-Antarctic environments and provide early warning indicators of significant environmental change.

Effects of temperature and salinity on the reproductive phases of Macrocystis pyrifera (L.) C. Agardh (Phaeophyceae) in the Magellan region

The region of Magallanes has the world’s largest sub-Antarctic environments, including the heterogeneous habitats of archipelagos, fjords, channels, and inlets formed by ice advancing and retreating during Quaternary glacial processes. In marine ecosystems, the temperature, salinity, and photoperiod are key parameters which delimit the survival, reproduction and development of the macroalgae and, therefore, the biogeography of numerous sub-Antarctic species. In this research, we compare the reproductive development patterns in spores of Macrocystis pyrifera coming from places with different salinities along longitudinal and latitudinal gradients in Skyring Sound, Otway Sound, the Strait of Magellan (Possession Bay and Puerto del Hambre), and the Beagle Channel (Paula Bay). Laboratory analyses included four salinities and two different temperatures, comparing the percentage of spore germination, sex ratio in females and male gametophytes, and the development of gametogenesis through the proportion of gametophytes and sporophytes, with a factorial experimental design. The best germination percentages were obtained in Puerto del Hambre; the best sex ratio, on the other hand, was in Skyring Sound; finaly, for gametogenesis development, the best results were obtained in Otway Sound and Possession Bay. We prove the temperature and salinity effect over the studied population; moreover, these results demonstrate that at the end of the cycle each population develops more effectively in their local conditions, evidence of a local adaptation in M. pyrifera populations living in contrasting sites in the same region. This is crucial to understand how these populations react to the effect of environmental stressors; furthermore, the selection of appropriate conditions is also an important factor for the future commercial cultivation management of these important macroalgae.

Predominance and high diversity of genes associated to denitrification in metagenomes of subantarctic coastal sediments exposed to urban pollution.

The aim of this work was to characterize the microbial nitrogen cycling potential in sediments from Ushuaia Bay, a subantarctic environment that has suffered a recent explosive demographic growth. Subtidal sediment samples were retrieved in triplicate from two urban points in the Bay, and analyzed through metagenomic shotgun sequencing. Sequences assigned to genes related to nitrification, nitrate reduction and denitrification were predominant in this environment with respect to metagenomes from other environments, including other marine sediments. The nosZ gene, responsible for nitrous oxide transformation into di-nitrogen, presented a high diversity. The majority of NosZ sequences were classified as Clade II (atypical) variants affiliated to different bacterial lineages such as Bacteroidetes, Chloroflexi, Firmicutes, Proteobacteria, Verrucomicrobia, as well as to Archaea. The analysis of a fosmid metagenomic library from the same site showed that the genomic context of atypical variants was variable, and was accompanied by distinct regulatory elements, suggesting the evolution of differential ecophysiological roles. This work increases our understanding of the microbial ecology of nitrogen transformations in cold coastal environments and provides evidence of an enhanced denitrification potential in impacted sediment microbial communities. In addition, it highlights the role of yet overlooked populations in the mitigation of environmentally harmful forms of nitrogen.

A new method for analysing and representing ground temperature variations in cold environments. The Fuegian Andes, Tierra del Fuego, Argentina

The thermal response of soils in cold environments has been investigated in numerous studies. The data considered here were obtained in a study carried out in Tierra del Fuego, Argentina, as part of the IV International Polar Year. Temperature sensors were installed at ground level (0) and depths of -10, -20 and -60 cm in the study area, with the aim of characterizing the thermal response by detecting diurnal and annual variations.The study has two main aims. The first is to present and discuss the study findings regarding the thermal response of a soil in a sub-Antarctic environment by using classical descriptive analysis. The second, closely related, aim is to apply some novel statistical tools that would help improve this description. The study of freeze-thaw patterns can be approached from a non-parametric perspective, while taking into account the cyclical nature of the data. Data are considered cyclical when they can be represented on a unit circle, as with the hours in which certain events occur throughout a day (e.g. freezing and thawing). Analysis of this type of data is very different from the analysis of scalar data, as regards both descriptive and graphical measures. The application in this study of methods used to represent and analyse cyclical data improved visualization of the data and interpretation of the analytical findings. The main contribution of the present study is the use of estimators of the nuclear type density and derived techniques, such as the CircSiZer map, which enabled identification of significant freeze-thaw patterns. In addition, the relationships between the temperature recordings at different points were analysed using Taylor diagrams.

Wind Distortion in Alpine and Subantarctic Plants is Constant among Life Forms but does not Necessarily Reflect Prevailing Wind Direction

ABSTRACTWoody plants in windy environments have been used as indicators of prevailing wind direction, because wind can influence plant growth form. We investigated whether non-woody plants also display consistent prevailing wind deformation by observing the direction of asymmetry in growth form of cushion plants, graminoids, and prostrate shrubs growing in highly wind-exposed treeless environments in alpine Tasmania and subantarctic Macquarie Island. Wind distortion of individual plants was inferred from vertical photographs of feldmark and alpine heath vegetation. High correspondence in growth direction between plants of different types suggests a uniform wind influence on plants at the local scale (within <2 m). Dominant wind direction inferred from plant distortion was not consistent with the strongest and most frequent winds. On a relatively dry mountain with shallow soils the plants responded to strong northwest winds in an apparent desiccation response. Elsewhere, they responded to strong southwest winds in an apparent ice abrasion response. We conclude that, in maritime alpine and subantarctic environments, the direction of wind distortion can be measured using any of shrubs, graminoids, or cushion plants, but that this direction is not necessarily a response to the prevailing strongest winds, but rather winds that most damage foliage, the cause of damage varying with environmental context.

Interpopulation variation in nest architecture in a secondary cavity-nesting bird suggests site-specific strategies to cope with heat loss and humidity

ABSTRACT Nest morphology can affect the breeding success of birds. Thus, birds inhabiting different environments may experience divergent selection for nest structure and composition that results in intraspecific geographic variation in nest architecture. We describe interpopulation differences in nest architecture among Thorn-tailed Rayaditos (Aphrastura spinicauda) in 2 contrasting environments near the species' distribution limits: a temperate and very humid environment in north-central Chile (the forest relicts of Fray Jorge National Park; 30°38′S, 71°40′W) and a cold and windy sub-Antarctic environment in the south of Chile (Isla Navarino; 55°4′S, 67°40′W). We collected a total of 62 nests from Fray Jorge and 61 nests from Navarino in 2013 and 2014, measured their dimensions, and quantified their constitutive materials. We tested the nests' thermal properties (simulating heat loss by convection and conduction) and hygroscopic features (water absorption and water loss capacity) and used general linear...