A new biologging approach reveals unique flightless molt strategies of Atlantic puffins

Animal- borne telemetry devices provide essential insights into the life- history strate -gies of far- ranging species and allow us to understand how they interact with their environment. Many species in the seabird family Alcidae undergo a synchronous molt of all primary flight feathers during the non- breeding season, making them flightless and more susceptible to environmental stressors, including severe storms and prey shortages. However, the timing and location of molt remain largely unknown, with most information coming from studies on birds killed by storms or shot by hunters for food. Using light- level geolocators with saltwater immersion loggers, we develop a method for determining flightless periods in the context of the annual cycle. Four Atlantic puffins (Fratercula arctica) were equipped with geolocator/immersion loggers on each leg to attempt to overcome issues of leg tucking in plumage while sitting on the water, which confounds the interpretation of logger data. Light- level and saltwa -ter immersion time- series data were combined to correct for this issue. This approach was adapted and applied to 40 puffins equipped with the standard practice deploy -ments of geolocators on one leg only. Flightless periods consistent with molt were identified in the dual- equipped birds, whereas molt identification in single- equippedbirds was less effective and definitive and should be treated with caution. Within the dual- equipped sample, we present evidence for two flightless molt periods per non- breeding season in two puffins that undertook more extensive migrations (>2000 km) and were flightless for up to 77 days in a single non- breeding season. A biannual flight feather molt is highly unusual among non- passerine birds and may be unique to birds that undergo catastrophic molt, i.e., become flightless when molting. Although our conclusions are based on a small sample, we have established a freely available meth -odological framework for future investigation of the molt patterns of this and other seabird species.auks, flightless molt, Fratercula, Geolocator tracking, life-history strategies, puffin, seabird ecology, wet–dry sensorpublishedVersio

Light-level geolocators reveal spatial variations in interactions between northern fulmars and fisheries

Seabird−fishery interactions are a common phenomenon of conservation concern. Here, we highlight how light-level geolocators provide promising opportunities to study these interactions. By examining raw light data, it is possible to detect encounters with artificial lights atnight, while conductivity data give insight on seabird behaviour during encounters. We used geolocator data from 336 northern fulmars Fulmarus glacialis tracked from 12 colonies in the North-East Atlantic and Barents Sea during the non-breeding season to (1) confirm that detections of artificial lights correspond to encounters with fishing vessels by comparing overlap between fishing effort and both the position of detections and the activity of birds during encounters, (2) assess spatial differences in the number of encounters among wintering areas and (3) test whethersome individuals forage around fishing vessels more often than others. Most (88.1%) of the track encountered artificial light at least once, with 9.5 ± 0.4 (SE) detections on average per 6 mo nonbreeding season. Encounters occurred more frequently where fishing effort was high, and birds from some colonies had higher probabilities of encountering lights at night. During encounters, fulmars spent more time foraging and less time resting, strongly suggesting that artificial lights reflect the activity of birds around fishing vessels. Inter-individual variability in the probability of encountering light was high (range: 0−68 encounters per 6 mo non-breeding season), meaning that some individuals were more often associated with fishing vessels than others, independently of their colony of origin. Our study highlights the potential of geolocators to study seabird−fisheryinteractions at a large scale and a low cost.publishedVersio

A new biologging approach reveals unique flightless molt strategies of Atlantic puffins

Animal-borne telemetry devices provide essential insights into the life-history strategies of far-ranging species and allow us to understand how they interact with their environment. Many species in the seabird family Alcidae undergo a synchronous molt of all primary flight feathers during the non-breeding season, making them flightless and more susceptible to environmental stressors, including severe storms and prey shortages. However, the timing and location of molt remain largely unknown, with most information coming from studies on birds killed by storms or shot by hunters for food. Using light-level geolocators with saltwater immersion loggers, we develop a method for determining flightless periods in the context of the annual cycle. Four Atlantic puffins (Fratercula arctica) were equipped with geolocator/immersion loggers on each leg to attempt to overcome issues of leg tucking in plumage while sitting on the water, which confounds the interpretation of logger data. Light-level and saltwater immersion time-series data were combined to correct for this issue. This approach was adapted and applied to 40 puffins equipped with the standard practice deployments of geolocators on one leg only. Flightless periods consistent with molt were identified in the dual-equipped birds, whereas molt identification in single-equipped birds was less effective and definitive and should be treated with caution. Within the dual-equipped sample, we present evidence for two flightless molt periods per non-breeding season in two puffins that undertook more extensive migrations (>2000 km) and were flightless for up to 77 days in a single non-breeding season. A biannual flight feather molt is highly unusual among non-passerine birds and may be unique to birds that undergo catastrophic molt, i.e., become flightless when molting. Although our conclusions are based on a small sample, we have established a freely available methodological framework for future investigation of the molt patterns of this and other seabird species

Six pelagic seabird species of the North Atlantic engage in a fly-and-forage strategy during their migratory movements

Bird migration is commonly defined as a seasonal movement between breeding and non-breeding grounds. It generally involves relatively straight and directed large-scale movements, with a latitudinal change, and specific daily activity patterns comprising less or no foraging and more traveling time. Our main objective was to describe how this general definition applies to seabirds. We investigated migration characteristics of 6 pelagic seabird species (little auk Alle alle, Atlantic puffin Fratercula arctica, common guillemot Uria aalge, Brünnich’s guillemot U. lomvia, black-legged kittiwake Rissa tridactyla and northern fulmars Fulmarus glacialis). We analysed an extensive geolocator positional and saltwater immersion dataset from 29 colonies in the North-East Atlantic and across several years (2008-2019). We used a novel method to identify active migration periods based on segmentation of time series of track characteristics (latitude, longitude, net-squared displacement). Additionally, we used the saltwater immersion data of geolocators to infer bird activity. We found that the 6 species had, on average, 3 to 4 migration periods and 2 to 3 distinct stationary areas during the non-breeding season. On average, seabirds spent the winter at lower latitudes than their breeding colonies and followed specific migration routes rather than non-directionally dispersing from their colonies. Differences in daily activity patterns were small between migratory and stationary periods, suggesting that all species continued to forage and rest while migrating, engaging in a ‘fly-and-forage’ migratory strategy. We thereby demonstrate the importance of habitats visited during seabird migrations as those that are not just flown over, but which may be important for re-fuelling.publishedVersio

Twilight foraging enables European shags to survive the winter across their latitudinal range

Species breeding at high latitudes face a significant challenge of surviving the winter. Such conditions are particularly severe for diurnal marine endotherms such as seabirds. A critical question is therefore what behavioural strategies such species adopt to maximise survival probability. We tested 3 hypotheses: (1) they migrate to lower latitudes to exploit longer day length (‘sun-chasing’), (2) they forage at night (‘night-feeding’), or (3) they target high-quality food patches to minimise foraging time (‘feasting’). We studied the winter migration and foraging strategies of European shags Phalacrocorax aristotelis from 6 colonies across a latitudinal gradient from temperate regions to north of the Arctic Circle using geolocators deployed over 11 winters. We found evidence for ‘sun-chasing’, whereby average southerly movements were greatest from colonies at higher latitudes. However, a proportion of individuals from higher latitudes remained resident in winter and, in the absence of daylight, they foraged during twilight and only very occasionally during the night. At lower latitudes, there was little evidence that individuals migrated south, nocturnal feeding was absent, and twilight feeding was infrequent, suggesting that there was sufficient daylight in winter. There was no evidence that winter foraging time was lowest at higher latitudes, as predicted by the ‘feasting’ hypothesis. Our results suggest that shags adopt different behavioural strategies to survive the winter across their latitudinal range, dictated by the differing light constraints. Our study highlights the value of multi-colony studies in testing key hypotheses to explain population persistence in seabird species that occur over large latitudinal ranges

Meeting Paris agreement objectives will temper seabird winter distribution shifts in the North Atlantic Ocean

We explored the implications of reaching the Paris Agreement Objective of limiting global warming to <2°C for the future winter distribution of the North Atlantic seabird community. We predicted and quantified current and future winter habitats of five North Atlantic Ocean seabird species (Alle alle, Fratercula arctica, Uria aalge, Uria lomvia and Rissa tridactyla) using tracking data for ~1500 individuals through resource selection functions based on mechanistic modeling of seabird energy requirements, and a dynamic bioclimate envelope model of seabird prey. Future winter distributions were predicted to shift with climate change, especially when global warming exceed 2°C under a “no mitigation” scenario, modifying seabird wintering hotspots in the North Atlantic Ocean. Our findings suggest that meeting Paris agreement objectives will limit changes in seabird selected habitat location and size in the North Atlantic Ocean during the 21st century. We thereby provide key information for the design of adaptive marine‐protected areas in a changing ocean

Effect of Manipulated Stress Levels of Adult Kittiwakes (Rissa tridactyla) on Offspring Immunocompetence

Low food availability increase food stress and can cause a shift of energy expenditure to invest in self-survival rather than reproductive effort in breeding Black-legged kittiwakes (Rissa tridactyla). This affects early development fitness in offspring, which impact on their long-term survival. The present study investigates effects of stress in adult kittiwakes on immunocompetence of offspring, which is recognized as important trait in long-term survival. Increased parental stress is predicted to negatively affect immunocompetence and body condition. To assess immunocompetence, a ratio between innate hetrophils and acquired lymphocytes were calculated, together with measured reactivity of natural antibodies and complement on foreign antigen. Data was collected over two breeding seasons in a medium sized colony on the west coast of Svalbard, Norway. In one season, parental stress was manipulated by exposing individuals for implants with exogenous corticosterone for a three day period. A control group was exposed to sham implants. Stress and body condition was recorded in parents and offspring, along with immunocompetence in offspring approximately 15 days after implants were removed. In the second season, data of the same measurements were collected without stress-manipulations. Both seasons provided normal foraging conditions. I found an unexpected decrease in baseline corticosterone in stress-manipulated individuals, with corticosterone values being 55% lower than that of sham- treated individuals at the latest point of sampling. Parental body condition was not affected by treatments. This was accompanied by a greater overall fitness in the offspring of stress- manipulated adults. Hence, my results support a fixed investment hypothesis , in which parental birds will increase their reproductive effort if food stress is decreased under normal foraging conditions. Immunocompetence was only partly affected by parental treatment, while body condition was significantly higher in chicks of corticosterone-implanted individuals. Hence, there was predicted a greater allocation of energy towards higher body condition, rather than immunocompetence. This might imply a higher selection for body condition during development, when provided normal conditions. This is the first study to present experimental data on immunocompetence in offspring of adult kittiwakes when the parental stress level is manipulated

Arctic-breeding seabirds’ hotspots in space and time - A methodological framework for year-round modelling of environmental niche and abundance using light-logger data

Fauchald, P., Tarroux, A., Bråthen, V. S., Descamps, S., Ekker, M., Helgason, H. H., Merkel, B., Moe, B., Åström, J., Strøm, H. 2019. Arctic-breeding seabirds’ hotspots in space and time -a methodological framework for year-round modelling of abundance and environmen-tal niche using light-logger data. NINA Report 1657. Norwegian Institute for Nature Re-search. By positioning a large number of seabirds throughout the year using miniaturized geoloca-tors (GLS), the SEATRACK program provides a unique dataset on the seasonal distribution of seabirds from colonies in Russia (Barents and White Seas), Norway (incl. Svalbard and Jan Mayen), Iceland, Faroe Islands and the British Isles. Combining this extensive dataset with data on population sizes has for the first time made it possible to develop seasonal estimates of the spatial distribution of Northeast Atlantic seabirds. In this report, we document the workflow and methods used to develop monthly estimates of the distribution of seabirds from colonies covered by the SEATRACK design. The work-flow presented here consists of three steps, starting from pre-processed GLS data. First, because the position data from the loggers represent “presence-only” data, it is vital to re-move sampling biases before using the data to make interpretations of the spatial distribu-tion. Therefore, in step 1 we developed a tailored algorithm, IRMA (Informed Random Move-ment Algorithm), to reduce biases and fill gaps in the dataset due to various factors such as polar day/night, equinox and positions over land. IRMA uses available information and data to triangulate new positions and does ultimately provide a dataset where sampling biases has been reduced to a minimum. In the next step, we combined the position dataset with environmental data to model the habitat of each SEATRACK colony throughout the year. Environmental variables included remote sensing data of oceanography and primary pro-duction, and data on bathymetry. We used standard Species Distribution Models (SDM) on presence-only data to model the habitat used by each SEATRACK colony in each month. Finally, in step 3 we combined the predictions from the habitat models with available data on the populations covered by the SEATRACK design to provide predictions on seabird spatial distribution and abundance. A colony database was compiled to address the popu-lation sizes, and spatial analyses were conducted to justify a distance-rule for assigning the colonies in the colony database to the nearest SEATRACK colony. Based on the distance rule, we predicted the habitat for each colony covered by the SEATRACK design and weighted the estimates with population size. According to the distance-rule, the SEATRACK design covered from 74% to 96% of the Northeast Atlantic populations, depending on spe-cies. Analyses and predictions were done for six common pelagic seabirds: Northern fulmar (Ful-marus glacialis), black-legged kittiwake (Rissa tridactyla), common guillemot (Uria aalge), Brünnich’s guillemot (Uria lomvia), little auk (Alle alle) and Atlantic puffin (Fratercula arctica). The resulting datasets represent monthly estimates of the number of birds from a specific breeding population in each cell of a 0.1° x 0.1° raster grid covering the entire North Atlantic. Monthly outputs were produced for each combination of species and colony, resulting in a dataset of more than 9619 raster maps. The gridded data are provided NetCDF files, one per species, and a short R-script is provided for reading, plotting and aggregating the data. An interactive mapping tool will be made available through the SEATRACK website. Appli-cations for the new tool include marine spatial planning, environmental impact- and risk as-sessments as well as assessments of seabird responses to environmental and climate change

An automated procedure (v2.0) to obtain positions from light-level geolocators in large-scale tracking of seabirds. A method description for the SEATRACK project

Bråthen, V.S., Moe, B., Amélineau, F., Ekker, M., Fauchald, P.,Helgason, H.H., Johansen, M. K., Merkel, B., Tarroux, A., Åström, J. & Strøm, H. 2021. An automated procedure (v2.0) to obtain positions from light-level geolocators in large-scale tracking of seabirds. A method description for the SEATRACK project. NINA Report 1893. Norwegian Institute for Nature Research. Partners in the SEATRACK project have since 2014 deployed >14 000 light-level geolocators on 11 species of seabirds to study their non-breeding distribution in the North Atlantic. Geolocator tags are ideal for large-scale tracking of seabirds being cheap and small. The tags contains a clock and a light sensor that register light levels at fixed intervals. These data are stored in the internal memory and are obtained when the tag is recovered from the bird. From these data two positions per day are calculated by estimating latitude from the length of day and night, and longitude from time of mid-day and mid-night. However, positions cannot be obtained from recorded light-data during the polar night or midnight sun. Further, the latitudinal accuracy is unreliable close to spring and autumn equinox when the length of day and night is similar across the earth. Using a threshold method, we first identify twilight events, which is the time when light-levels cross a predefined threshold that separate day from night. However, the light-level recordings are affected by environmental factors and the behaviour of the bird that may shade the geolocator or expose it to artificial light. As such, the accuracy is low compared to GPS or Argos tracking devices. A common approach has therefore been to improve the identification of these twilight events by manually inspecting the light-level data. This process is, however, time-consuming and prone to not being fully consistent and reproducible among different persons applying it. In this report, we describe an automated procedure (v2.0) for obtaining the basic positional dataset in SEATRACK from raw light-level data. The procedure automatically filters and edits the twilight events used for calculating positions. It further removes unrealistic positions using filters on equinox periods, speed, distribution, angle, distance, variation in timing of twilights and midnight sun periods, and produces double smoothed positions. Calibration of sun elevation angles, crucial for producing the final positions, is performed on each track and is the only part involving subjective assessment, but we show that it can be performed consistently and with a high repeatability. SEATRACK processes light data from >1000 geolocators after each field season, and the database has become one of the largest seabird tracking databases in the world. The automated procedure (v2.0) is a very cost-efficient method for such large-scale tracking and is consistent and reproducible. We have recently updated the entire database using this procedure, replacing all previous data based on the manual procedure and the first version of the automated procedure (v1.0). This report describes the methods used to obtain positions from geolocators in the SEATRACK project. As the described procedure replace our previous manual method, we show comparisons of the two procedures. The report also provides examples of how to read and visualize the positional data and can serve as the reference for the methods and as a tool for using the data