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- Data packageData from: A multi-scale test of the forage maturation hypothesis in a partially migratory ungulate population(2016-01-29) Hebblewhite, Mark; Merrill, EvelynThe forage maturation hypothesis (FMH) proposes that ungulate migration is driven by selection for high forage quality. Because quality declines with plant maturation, but intake declines at low biomass, ungulates are predicted to select for intermediate forage biomass to maximize energy intake by following phenological gradients during the growing season. We tested the FMH in the Canadian Rocky Mountains by comparing forage availability and selection by both migrant and nonmigratory resident elk (Cervus elaphus) during three growing seasons from 2002–2004. First, we confirmed that the expected trade-off between forage quality and quantity occurred across vegetation communities. Next, we modeled forage biomass and phenology during the growing season by combining ground and remote-sensing approaches. The growing season started 2.2 days earlier every 1 km east of the continental divide, was delayed by 50 days for every 1000-m increase in elevation, and occurred 8 days earlier on south aspects. Migrant and resident selection for forage biomass was then compared across three spatial scales (across the study area, within summer home ranges, and along movement paths) using VHF and GPS telemetry locations from 119 female elk. Migrant home ranges occurred closer to the continental divide in areas of higher topographical diversity, resulting in migrants consistently selecting for intermediate biomass at the two largest scales, but not at the finest scale along movement paths. In contrast, residents selected maximum forage biomass across all spatial scales. To evaluate the consequences of selection, we compared exposure at telemetry locations of migrant and resident elk to expected forage biomass and digestibility. The expected digestibility for migrant elk in summer was 6.5% higher than for residents, which was corroborated with higher fecal nitrogen levels for migrants. The observed differences in digestibility should increase migrant elk body mass, pregnancy rates, and adult and calf survival rates. Whether bottom-up effects of improved forage quality are realized will ultimately depend on trade-offs between forage and predation. Nevertheless, this study provides comprehensive evidence that montane ungulate migration leads to greater access to higher-quality forage relative to nonmigratory congeners, as predicted by the forage maturation hypothesis, resulting primarily from large-scale selection patterns.
- Data packageData from: A note on the reestablishment of the cheetah population in the Pilanesberg National Park, South Africa(2020-11-25) Power, R. John; Dell, StephenThe establishment of protected areas is recognized as a means to conserve large mammal species, and cheetah (Acinonyx jubatus) conservation is well served by these protected areas. The Pilanesberg National Park (Pilanesberg) is one such reserve within the managed metapopulation. Here, we firstly document the reproductive success of a single reintroduced female cheetah and, secondly, discuss the population's recovery in the context of the managed metapopulation. In April 2014, Pilanesberg had three adult cheetahs; the newly reintroduced female and the coalition of two adult males. The focal study animal was this adult female that was initially held in a boma at Madikwe Game Reserve for ∼3 months and ‘hard released’ into Pilanesberg with a fitted satellite collar. She was monitored by the first and fifth authors on a daily and monthly basis by satellite and radio-telemetry, respectively; while all cheetahs were also monitored by opportunistic observations by tourists and guides.
- Data packageData from: A novel approach to quantifying the spatiotemporal behavior of instrumented grey seals used to sample the environment(2015-09-15) Lidgard, Damian C.; Bowen, W. Don; Iverson, Sara J.Background: Paired with satellite location telemetry, animal-borne instruments can collect spatiotemporal data describing the animal’s movement and environment at a scale relevant to its behavior. Ecologists have developed methods for identifying the area(s) used by an animal (e.g., home range) and those used most intensely (utilization distribution) based on location data. However, few have extended these models beyond their traditional roles as descriptive 2D summaries of point data. Here we demonstrate how the home range method, T-LoCoH, can be expanded to quantify collective sampling coverage by multiple instrumented animals using grey seals (Halichoerus grypus) equipped with GPS tags and acoustic transceivers on the Scotian Shelf (Atlantic Canada) as a case study. At the individual level, we illustrate how time and space-use metrics quantifying individual sampling coverage may be used to determine the rate of acoustic transmissions received. Results: Grey seals collectively sampled an area of 11,308 km 2 and intensely sampled an area of 31 km 2 from June-December. The largest area sampled was in July (2094.56 km 2 ) and the smallest area sampled occurred in August (1259.80 km 2 ), with changes in sampling coverage observed through time. Conclusions: T-LoCoH provides an effective means to quantify changes in collective sampling effort by multiple instrumented animals and to compare these changes across time. We also illustrate how time and space-use metrics of individual instrumented seal movement calculated using T-LoCoH can be used to account for differences in the amount of time a bioprobe (biological sampling platform) spends in an area.
- Data packageData from: A pan-European, multi-population assessment of migratory connectivity in a near-threatened migrant bird(2015-07-22) Finch, Tom; Saunders, Philip; Catry, Inês; Mardega, Ieva; Mayet, Patrick; Račinskis, Edmunds; Sackl, Peter; Schwartz, Timothée; Tiefenbach, Michael; Hewson, Chris; Franco, Aldina; Butler, Simon JamesAim: The extent to which individuals from different breeding populations mix throughout the non-breeding season (i.e. ‘migratory connectivity’) has important consequences for population dynamics and conservation. Given recent declines of long-distance migrant birds, multi-population tracking studies are crucial in order to assess the strength of migratory connectivity and to identify key sites en route. Here, we present the first large-scale analysis of migration patterns and migratory connectivity in the globally near-threatened European roller Coracias garrulus. Location: Breeding area: Europe; passage area: Mediterranean, sub-Saharan Africa, Arabian Peninsula; wintering area: southern Africa Methods: We synthesise new geolocator data with existing geolocator, satellite tag and ring recovery data from eight countries across Europe. We describe routes and stopover sites, analyse the spatial pattern of winter sites with respect to breeding origin, and quantify the strength of connectivity between breeding and winter sites. Results: We demonstrate the importance of the northern savannah zone as a stopover region and reveal the easterly spring loop (via Arabia) and leap-frog migration of rollers from eastern populations. Whilst there was some overlap between individuals from different populations over winter, their distribution was non-random, with positive correlations between breeding and autumn/winter longitude as well as between pairwise distance matrices of breeding and winter sites. Connectivity was stronger for eastern populations than western ones. Main conclusions: The moderate levels of connectivity detected here may increase the resilience of breeding populations to localised habitat loss on the winter quarters. We also highlight passage regions crucial for the successful conservation of Roller populations, including the Sahel/Sudan savannah for all populations, and the Horn of Africa/Arabian Peninsula for north-eastern rollers.
- Data packageData from: A periodic Markov model to formalise animal migration on a network [white-fronted goose data](2018-06-13) Kruckenberg, Helmut; Müskens, Gerhard J.D.M.; Ebbinge, Barwolt S.NOTE: A portion of these same individuals and data are also published with doi 10.5441/001/1.31c2v92f. Regular, long-distance migrations of thousands of animal species have consequences for the ecosystems that they visit, modifying trophic interactions and transporting many non-pathogenic and pathogenic organisms. The spatial structure and dynamic properties of animal migrations and population flyways largely determine those trophic and transport effects, but are yet poorly studied. As a basis, we propose a periodic Markov model on the spatial migration network of breeding, stopover and wintering sites to formally describe the process of animal migration on the population level. From seasonally changing transition rates we derived stable, seasonal densities of animals at the network nodes. We parametrized the model with high-quality GPS and satellite telemetry tracks of white storks (Ciconia ciconia) and greater white-fronted geese (Anser a. albifrons). Topological and network flow properties of the two derived networks conform to migration properties like seasonally changing connectivity and shared, directed movement. Thus, the model realistically describes the migration movement of complete populations and can become an important tool to study the effects of climate and habitat change and pathogen spread on migratory animals. Furthermore, the property of periodically changing transition rates makes it a new type of complex model and we need to understand its dynamic properties.
- Data packageData from: A pilot study on the home range and movement patterns of the Andean Fox Lycalopex culpaeus (Molina, 1782) in Cotopaxi National Park, Ecuador(2021-09-02) Castellanos, ArmandoThis study reports movement patterns and home range estimates of an Andean fox (Lycalopex culpaeus) in Cotopaxi National Park in Ecuador, representing the first GPS-tagging of the species. The GPS functioned well during the 197-day tracking period. Home range sizes ranged between 4.9 and 8.1 km2, depending on the estimation method. Movement speeds averaged 0.17 km/h at day versus 0.87 km/h at night, and distance traveled averaged 0.23 km at day versus 0.89 km at night. These preliminary results highlight the importance of collecting unbiased, high-quality data which enables an enhanced understanding on mammal behavior and human/animal interaction.
- Data packageData from: Acoustic evaluation of behavioral states predicted from GPS tracking: a case study of a marine fishing bat(2019-06-26) Hurme, Edward; Gurarie, Eliezer; Greif, Stefan; Herrera M., L. Gerardo; Flores-Martínez, José Juan; Wilkinson, Gerald S.; Yovel, YossiBackground: Multiple methods have been developed to infer behavioral states from animal movement data, but rarely has their accuracy been assessed from independent evidence, especially for location data sampled with high temporal resolution. Here we evaluate the performance of behavioral segmentation methods using acoustic recordings that monitor prey capture attempts. Methods: We recorded GPS locations and ultrasonic audio during the foraging trips of 11 Mexican fish-eating bats, Myotis vivesi, using miniature bio-loggers. We then applied five different segmentation algorithms (k-means clustering, expectation-maximization and binary clustering, first-passage time, hidden Markov models, and correlated velocity change point analysis) to infer two behavioral states, foraging and commuting, from the GPS data. To evaluate the inference, we independently identified characteristic patterns of biosonar calls (“feeding buzzes”) that occur during foraging in the audio recordings. We then compared segmentation methods on how well they correctly identified the two behaviors and if their estimates of foraging movement parameters matched those for locations with buzzes. Results: While the five methods differed in the median percentage of buzzes occurring during predicted foraging events, or true positive rate (44–75%), a two-state hidden Markov model had the highest median balanced accuracy (67%). Hidden Markov models and first-passage time predicted foraging flight speeds and turn angles similar to those measured at locations with feeding buzzes and did not differ in the number or duration of predicted foraging events. Conclusion: The hidden Markov model method performed best at identifying fish-eating bat foraging segments; however, first-passage time was not significantly different and gave similar parameter estimates. This is the first attempt to evaluate segmentation methodologies in echolocating bats and provides an evaluation framework that can be used on other species.
- Data packageData from: Airplane tracking documents the fastest flight speeds recorded for bats(2016-10-31) McCracken, Gary; Safi, Kamran; Kunz, Thomas; Dechmann, Dina K.N.; Swartz, Sharon; Wikelski, MartinThe performance capabilities of flying animals reflect the interplay of biomechanical and physiological constraints and evolutionary innovation. Of the two extant groups of vertebrates that are capable of powered flight, birds are thought to fly more efficiently and faster than bats. However, fast-flying bat species that are adapted for flight in open airspace are similar in wing shape and appear to be similar in flight dynamics to fast-flying birds that exploit the same aerial niche. Here, we investigate flight behaviour in seven free-flying Brazilian free-tailed bats (Tadarida brasiliensis) and report that the maximum ground speeds achieved exceed speeds previously documented for any bat. Regional wind modelling indicates that bats adjusted flight speeds in response to winds by flying more slowly as wind support increased and flying faster when confronted with crosswinds, as demonstrated for insects, birds and other bats. Increased frequency of pauses in wing beats at faster speeds suggests that flap-gliding assists the bats’ rapid flight. Our results suggest that flight performance in bats has been underappreciated and that functional differences in the flight abilities of birds and bats require re-evaluation.
- Data packageData from: Allometric and temporal scaling of movement characteristics in Galapagos tortoises(2016-06-29) Bastille-Rousseau, Guillaume; Yackulic, Charles B.; Frair, Jacqueline L.; Cabrera, Freddy; Blake, StephenNOTE: An updated and larger version of this dataset is available. See https://doi.org/10.5441/001/1.6gr485fk. ABSTRACT: (1) Understanding how individual movement scales with body size is of fundamental importance in predicting ecological relationships for diverse species. One-dimensional movement metrics scale consistently with body size yet vary over different temporal scales. Knowing how temporal scale influences the relationship between animal body size and movement would better inform hypotheses about the efficiency of foraging behaviour, the ontogeny of energy budgets, and numerous life history trade-offs. (2) We investigated how the temporal scaling of allometric patterns in movement vary over the course of a year, specifically during periods of motivated (directional and fast movement) and unmotivated (stationary and tortuous movement) behaviour. We focused on a recently diverged group of species that displays wide variation in movement behaviour—giant Galapagos tortoises (Chelonoidis spp.)—to test how movement metrics estimated on a monthly basis scaled with body size. (3) We used state-space modelling to estimate seven different movement metrics of Galapagos tortoises. We used log-log regression of the power law to evaluate allometric scaling for these movement metrics, and contrasted relationships by species and sex. (4) Allometric scaling of movement was more apparent during motivated periods of movement. During this period, allometry was revealed at multiple temporal intervals (hourly, daily, and monthly), with values observed at daily and monthly intervals corresponding most closely to the expected ¼ scaling coefficient, albeit with wide credible intervals. We further detected differences in the magnitude of scaling among taxa uncoupled from observed differences in the temporal structuring of their movement rates. (5) Our results indicate that the definition of temporal scales is fundamental to the detection of allometry of movement, and should be given more attention in movement studies. Our approach not only provides new conceptual insights into temporal attributes in one-dimensional scaling of movement, but also generates valuable insights into the movement ecology of iconic yet poorly understood Galapagos giant tortoises.
- Data packageData from: Ámbito de hogar y actividad circadiana del ocelote (Leopardus pardalis) en la Isla de Barro Colorado, Panamá(2020-07-03) Moreno, Ricardo; Mares, Rafael; Aliaga-Rossel, Enzo; Kays, RolandBecause ocelots (Leopardus pardalis) are elusive species in the wild, little is known of them. This study determines the home range and circadian activity of this feline in the Barro Colorado Island (BCI), Panama. This island has a wet tropical rainforest. Using wooden box traps and Tomahawk traps, between July 2001 and May 2004 15 ocelots were captured, and three other ocelots in 2009. Once captured, they were sedated and VHF collars were fitted, for the ones captured in 2009 we fitted GPS collars. Camera-traps were used to get additional information from individuals without collars and a more reliable data interpretation. The average home range of ocelots, obtained by radio-telemetry was 3.48 km2 (DE: 3.17) for males and 1.48 km2 (DE: 0.65) for females, although an adult male used an area of 9 km2. Males traveled on average 1.15 km per day and females 0.7 km. Through telemetry and camera traps, we found that ocelots were primarily nocturnal (Night = 63.2%; Day = 36.8%). Our results are similar to other studies; however, they suggest that BCI ocelots have smaller home ranges due to the high availability of food and also by the high density of females within the home ranges of males.
- Data packageData from: An integrated approach to modeling grazing pressure in pastoral systems: the case of the Logone Floodplain (Cameroon)(2018-03-28) Moritz, MarkThe discussion about the impact of pastoral systems on ecosystems has been profoundly shaped by Hardin’s “tragedy of the commons” argument that held pastoralists responsible for overgrazing the range. Recent studies have shown that grazing ecosystems are much more complex and dynamic than was previously assumed and that pastoralists adaptively manage these systems. However, we still have little understanding how everyday herding affects ecosystems at the landscape level. We conducted a study of daily herd movements and grazing strategies in a mobile pastoral system in the Logone floodplain, Cameroon. We integrated GPS/GIS technology, video recordings of animal behavior, and ethnographic methods to develop a more accurate measurement of grazing pressure that takes into account both livestock densities and grazing behavior. We used the resulting grazing pressure data to evaluate existing conceptual models of grazing pressure at a landscape level. We found that models that predict that grazing pressure is skewed towards the direction of water most accurately reflect the situation in the Logone floodplain in the dry season. However, we found that the higher grazing pressure is not only the result of a higher density of cattle but also a change in the grazing behavior of animals after watering. Finally, we caution that the models of grazing pressure in the dry season cannot simply be extrapolated to the landscape level because mobile pastoralists do not remain in one central place.
- Data packageData from: Animal behavior, cost-based corridor models, and real corridors(2013-07-02) LaPoint, Scott; Gallery, Paul; Wikelski, Martin; Kays, RolandCorridors are popular conservation tools because they are thought to allow animals to safely move between habitat fragments, thereby maintaining landscape connectivity. Nonetheless, few studies show that mammals actually use corridors as predicted. Further, the assumptions underlying corridor models are rarely validated with field data. We categorized corridor use as a behavior, to identify animal-defined corridors, using movement data from fishers (Martes pennanti) tracked near Albany, New York, USA. We then used least-cost path analysis and circuit theory to predict fisher corridors and validated the performance of all three corridor models with data from camera traps. Six of eight fishers tracked used corridors to connect the forest patches that constitute their home ranges, however the locations of these corridors were not well predicted by the two cost-based models, which together identified only 5 of the 23 used corridors. Further, camera trap data suggest the cost-based corridor models performed poorly, often detecting fewer fishers and mammals than nearby habitat cores, whereas camera traps within animal-defined corridors recorded more passes made by fishers, carnivores, and all other non-target mammal groups. Our results suggest that (1) fishers use corridors to connect disjunct habitat fragments, (2) animal movement data can be used to identify corridors at local scales, (3) camera traps are useful tools for testing corridor model predictions, and (4) that corridor models can be improved by incorporating animal behavior data. Given the conservation importance and monetary costs of corridors, improving and validating corridor model predictions is vital.
- Data packageData from: Anosmia impairs homing orientation but not foraging behaviour in free-ranging shearwaters(2017-09-02) Padget, Oliver; Dell'Ariccia, Gaia; Gagliardo, Anna; González-Solís, Jacob; Guilford, TimShearwaters deprived of their olfactory sense before being displaced to distant sites have impaired homing ability but it is unknown what the role of olfaction is when birds navigate freely without their sense of smell. Furthermore, treatments used to induce anosmia and to disrupt magneto-reception in displacement experiments might influence non-specific factors not directly related to navigation and, as a consequence, the results of displacement experiments can have multiple interpretations. To address this, we GPS-tracked the free-ranging foraging trips of incubating Scopoli’s shearwaters within the Mediterranean Sea. As in previous experiments, shearwaters were either made anosmic with 4% zinc sulphate solution, magnetically impaired by attachment of a strong neodymium magnet or were controls. We found that birds from all three treatments embarked on foraging trips, had indistinguishable at-sea schedules of behaviour and returned to the colony having gained mass. However, we found that in the pelagic return stage of their foraging trips, anosmic birds were not oriented towards the colony but that coastal navigation was unaffected. These results support the case for zinc sulphate having a specific effect on the navigational ability of shearwaters and thus the view that seabirds consult an olfactory map to guide them across seascapes.
- Data packageData from: Are movements of day- and night-time passerine migrants as different as day and night?(2020-09-08) Michalik, Bianca; Brust, Vera; Hueppop, OmmoEven after decades of research, the migration of songbirds still holds numerous secrets. Distinct stopover and routing behavior of diurnally and nocturnally migrating songbirds has been stated in the 1960s, but empirical confirmation is yet lacking widely. We studied the behavior of individual diurnally migrating dunnocks and nocturnally migrating blackcaps by means of large‐scale automated radio‐telemetry. Birds were radio‐tagged during their stopover at the German North Sea coast. Our data indicate longer initial stopover duration in the diurnally migrating dunnocks, opposing the hypothesis of nocturnal migrants needing more time to recover due to their longer migratory flights. Nonetheless, dunnocks stopped over more often along their tracks as when compared to the nocturnally migrating blackcaps. Behavior en route did not differ as clearly between species challenging the general view of contrasting routings of diurnal and nocturnal migrants with regard to landscape and open water. Our results imply additional factors of relevance other than differences in species or daily migration timing per se. We discuss and highlight the need of detailed and individual based data to better understand stopover and routing behavior of songbirds in the environmental context.
- Data packageData from: As the duck flies: estimating the dispersal of low-pathogenic avian influenza viruses by migrating mallards(2018-11-26) van Toor, Mariëlle L.; Ottosson, Ulf; van der Meer, Tim; van Hoorn, Sita; Waldenström, JonasMany pathogens rely on the mobility of their hosts for dispersal. In order to understand and predict how a disease can rapidly sweep across entire continents, illuminating the contributions of host movements to disease spread is pivotal. While elegant proposals have been made to elucidate the spread of human infectious diseases, the direct observation of long-distance dispersal events of animal pathogens is challenging. Pathogens like avian influenza A viruses, causing only short disease in their animal hosts, have proven exceptionally hard to study. Here, we integrate comprehensive data on population and disease dynamics for low-pathogenic avian influenza viruses in one of their main hosts, the mallard, with a novel movement model trained from empirical, high-resolution tracks of mallard migrations. This allowed us to simulate individual mallard migrations from a key stopover site in the Baltic Sea for the entire population and link these movements to infection simulations. Using this novel approach, we were able to estimate the dispersal of low-pathogenic avian influenza viruses by migrating mallards throughout several autumn migratory seasons and predicted areas that are at risk of importing these viruses. We found that mallards are competent vectors and on average dispersed viruses over distances of 160 km in just three hours. Surprisingly, our simulations suggest that such dispersal events are rare even throughout the entire autumn migratory season. Our approach directly combines simulated population-level movements with local infection dynamics and offers a potential converging point for movement and disease ecology.
- Data packageData from: At-sea distribution and prey selection of Antarctic petrels and commercial krill fisheries(2016-10-10) Descamps, Sébastien; Tarroux, Arnaud; Cherel, Yves; Delord, Karine; Godø, Olaf R.; Kato, Akiko; Krafft, Bjørn A.; Lorentsen, Svein-Håkon; Ropert-Coudert, Yan; Skaret, Georg; Varpe, ØysteinCommercial fisheries may impact marine ecosystems and affect populations of predators like seabirds. In the Southern Ocean, there is an extensive fishery for Antarctic krill Euphausia superba that is projected to increase further. Comparing distribution and prey selection of fishing operations versus predators is needed to predict fishery-related impacts on krill-dependent predators. In this context, it is important to consider not only predators breeding near the fishing grounds but also the ones breeding far away and that disperse during the non-breeding season where they may interact with fisheries. In this study, we first quantified the overlap between the distribution of the Antarctic krill fisheries and the distribution of a krill dependent seabird, the Antarctic petrel Thalassoica antarctica, during both the breeding and non-breeding season. We tracked birds from the world biggest Antarctic petrel colony (Svarthamaren, Dronning Maud Land), located >1000 km from the main fishing areas, during three consecutive seasons. The overall spatial overlap between krill fisheries and Antarctic petrels was limited but varied greatly among and within years, and was high in some periods during the non-breeding season. In a second step, we described the length frequency distribution of Antarctic krill consumed by Antarctic petrels, and compared this with results from fisheries, as well as from diet studies in other krill predators. Krill taken by Antarctic petrels did not differ in size from that taken by trawls or from krill taken by most Antarctic krill predators. Selectivity for specific Antarctic krill stages seems generally low in Antarctic predators. Overall, our results show that competition between Antarctic petrels and krill fisheries is currently likely negligible. However, if krill fisheries are to increase in the future, competition with the Antarctic petrel may occur, even with birds breeding thousands of kilometers away.
- Data packageData from: At-sea distribution of spectacled eiders: a 120-year-old mystery resolved(2016-12-19) Petersen, Margaret R.; Douglas, David C.NOTE: An updated and larger version of this dataset is available through the US Geological Survey Alaska Science Center. See https://doi.org/10.5066/P9B091HG. ABSTRACT: The at-sea distribution of the threatened Spectacled Eider (Somateria fischeri) has remained largely undocumented. We identified migration corridors, staging and molting areas, and wintering areas of adult Spectacled Eiders using implanted satellite transmitters in birds from each of the three extant breeding grounds (North Slope and Yukon-Kuskokwim Delta in Alaska and arctic Russia). Based on transmitter locations, we conducted aerial surveys to provide visual confirmation of eider flocks and to estimate numbers of birds. We identified two principal molting and staging areas off coastal Alaska (Ledyard Bay and eastern Norton Sound) and two off coastal Russia (Mechigmenskiy Bay on the eastern Chukotka Peninsula, and the area between the Indigirka and Kolyma deltas in the Republic of Sakha). We estimated that >10,000 birds molt and stage in monospecific flocks at Mechigmenskiy and Ledyard bays, and several thousand molt and stage in eastern Norton Sound. We further identified eastern Norton Sound as the principal molting and staging area for females nesting on the Yukon-Kuskokwim Delta, and Ledyard Bay and Mechigmenskiy Bay as the principal molting and staging areas for females nesting on the North Slope. Males marked at all three breeding grounds molt and stage in Mechigmenskiy Bay, Ledyard Bay, and the Indigirka-Kolyma delta region. Males from the Yukon-Kuskokwim Delta molt and stage mainly at Mechigmenskiy Bay. Equal numbers of males from the North Slope molt and stage at all three areas, and most males from arctic Russia molt and stage at the Indigirka-Kolyma delta region. Postbreeding migration corridors were offshore in the Bering, Chukchi, and Beaufort seas. In winter, eiders were in the Bering Sea south of St. Lawrence Island. Our estimates from surveys in late winter and early spring suggest that at least 333,000 birds winter in single-species flocks in the pack ice in the Bering Sea.
- Data packageData from: Automated telemetry reveals age specific differences in flight duration and speed are driven by wind conditions in a migratory songbird(2015-09-24) Mitchell, Greg W.; Woodworth, Bradley K.; Taylor, Philip D.; Norris, D. RyanBackground: Given that winds encountered on migration could theoretically double or half the energy expenditure of aerial migrants, there should be strong selection on behaviour in relation to wind conditions aloft. However, evidence suggests that juvenile songbirds are less choosey about wind conditions at departure relative to adults, potentially increasing energy expenditure during flight. To date, there has yet to be a direct comparison of flight efficiency between free-living adult and juveniles songbirds during migration in relation to wind conditions aloft, likely because of the challenges of following known aged individual songbirds during flight. We used an automated digital telemetry array to compare the flight efficiency of adult and juvenile Savannah sparrows (Passerculus sandwichensis) as they flew nearly 100 km during two successive stages of their fall migration; a departure flight from their breeding grounds out over the ocean and then a migratory flight along a coast. Using a multilevel path modelling framework, we evaluated the effects of age, flight stage, tailwind component, and crosswind component on flight duration and groundspeed. Results: We found that juveniles departed under wind conditions that were less supportive relative to adults and that this resulted in juveniles taking 1.4 times longer to complete the same flight trajectories as adults. We did not find an effect of age on flight duration or groundspeed after controlling for wind conditions aloft, suggesting that both age groups were flying at similar airspeeds. We also found that groundspeeds were 1.7 times faster along the coast than over the ocean given more favourable tailwinds along the coast and because birds appeared to be climbing in altitude over the ocean, diverting some energy from horizontal to vertical movement. Conclusions: Our results provide the first direct evidence that adult songbirds have considerably more efficient migratory flights than juveniles, and that this efficiency is driven by the selection of more supportive tailwind conditions aloft. Given the importance of wind for efficient flight, we suggest this behaviour could be adaptive in juveniles, if for example, the benefits of a more flexible departure schedule outweigh the costs of flying with less supportive winds.
- Data packageData from: Autumn migration and wintering site of a wood warbler Phylloscopus sibilatrix breeding in Denmark identified using geolocation(2018-11-28) Tøttrup, Anders P.; Pedersen, Lykke; Thorup, KasperBackground: Basic knowledge of detailed spatiotemporal migration patterns is lacking for most migratory bird species. Using the smallest available geolocator, we aim to map autumn migration and wintering areas of north European wood warblers Phylloscopus sibilatrix and compare the spatiotemporal pattern with recoveries of individuals ringed across Europe. Results: A tracked wood warbler migrated south-south-east to sub-Saharan Africa in Sudan and then west-south-west to winter in Côte d’Ivoire. The timing and route fits well within the distribution of ring recoveries although the westward movement after the Sahara crossing is not revealed by the ring recoveries, but only few recoveries south of Sahara exist. Conclusions: The surprising westward movement south of the Sahara supplements the overall pattern revealed by ring recoveries and aids our understanding of the connectivity and site dependence in this generally declining species.
- Data packageData from: Behavioural adaptations to flight into thin air(2016-10-24) Sherub, Sherub; Wikelski, Martin; Fiedler, Wolfgang; Davidson, Sarah C.Soaring raptors can fly at high altitudes of up to 9000 m. The behavioural adjustments to high-altitude flights are largely unknown. We studied thermal- ling flights of Himalayan vultures (Gyps himalayensis) from 50 to 6500 m above sea level, a twofold range of air densities. To create the necessary lift to support the same weight and maintain soaring flight in thin air birds might modify lift coefficient by biophysical changes, such as wing posture and increasing the power expenditure. Alternatively, they can change their flight characteristics. We show that vultures use the latter and increase circle radius by 35% and airspeed by 21% over their flight altitude range. These simple behavioural adjustments enable vultures to move seamlessly during their annual migrations over the Himalaya without increasing energy output to flight in high elevations.