scholarly journals When to depart from a stopover site? Time since arrival matters more than current weather conditions

The Auk ◽  
2021 ◽  
Author(s):  
Sébastien Roques ◽  
Pierre-Yves Henry ◽  
Gaétan Guyot ◽  
Bruno Bargain ◽  
Emmanuelle Cam ◽  
...  
Keyword(s):  
Migratory Birds ◽  
Internal State ◽  
Weather Conditions ◽  
Fine Tuning ◽  
Fuel Loading ◽  
Modeling Framework ◽  
Long Distance ◽  
Stopover Site ◽  
Departure Probability ◽  
Breeding Migration

Abstract On the journey to wintering sites, most migratory birds alternate between flights and stopovers, where they rest and refuel. In contrast to the time-minimization strategy commonly assumed to drive the pre-breeding migration, birds are rather expected to follow an energy minimization during post-breeding migration. It is the cumulative duration of flights and stopovers that determines the total energy requirements and duration of the journey. Since migrating birds actually spend most of the time at stopovers sites, selection to minimize the amount of energy or time spent on migration is likely to operate on the effectiveness of stopover rest and refueling. Here, we address the relative contribution of factors acting on departure decisions from a stopover site during the post-breeding migration in a long-distance migratory songbird. When capture probability is low, it is impossible to measure fattening over the entire duration of the stopover. To get around this limitation, we use time since arrival (TSA) as a proxy for the progressive temporal change occurring in the internal state of an individual (i.e. rest, physiological recovery, and fuel loading) during the stopover. We develop a capture–recapture model to address the respective effects of estimated TSA and of weather conditions on departure probability. Using a 20-year dataset for Sedge Warblers (Acrocephalus schoenobaenus), we show that TSA served as a surrogate of the most important information that birds use when deciding to depart from a stopover site, while low humidity and rising atmospheric pressure only slightly increase daily departure probability. Hence, a bird would resume migration mainly according to the time it had to rest and refuel, and then fine-tuning departure decision according to weather conditions. The generality of these results needs to be assessed by applying this modeling framework to other migratory species and at sites or times with greater weather variability.

scholarly journals When to depart from a stopover site? Time-since-arrival matters more than current weather conditions

2020 ◽  
Author(s):  
Sebastien Roques ◽  
Pierre-Yves Henry ◽  
Gaetan Guyot ◽  
Bruno Bargain ◽  
Emmanuelle Cam ◽  
...  
Keyword(s):  
Migratory Birds ◽  
Total Duration ◽  
Weather Conditions ◽  
Long Distance ◽  
Migration Strategy ◽  
Stopover Site ◽  
Relative Contribution ◽  
Departure Probability ◽  
Breeding Migration ◽  
Migrating Birds

On the journey to wintering sites, migratory birds usually alternate between flights and stopovers where they rest and refuel. Migration strategies are assumed to differ according to season: a time-minimization pre-breeding migration strategy towards breeding locations, and an energy-minimization post-breeding migration strategy to wintering ones. The duration of flights and stopovers determines the energy requirements and the total duration of the journey. Since migrating birds actually spend most of the time at stopovers, selection to minimize the amount of energy or time spent on migration is very likely to operate on the effectiveness of stopover rest and refueling. Here we address the relative contribution of factors to departure decisions from stopover sites during the post-breeding migration in a long-distance migratory songbird. When capture probability is low it is impossible to assess the variation in body condition over the entire duration of the stopover. To get around this, we use Time Since Arrival (TSA) as a proxy for the changes in the state of individuals during the stopover. We propose that TSA is an integrative proxy for resting, feeding and fattening efficiency. We develop a capture-recapture model to address the relationship between departure probability, estimated TSA, and weather conditions. Using a 20-year dataset from sedge warblers, we show that TSA has a larger effect on departure probability than weather conditions. Low humidity and an increase in atmospheric pressure in the days preceding departure are associated with higher departure probability, but these effects are smaller than that of TSA.

scholarly journals Phenological trends in the pre‐ and post‐breeding migration of long‐distance migratory birds

2021 ◽  
Author(s):  
Kieran B. Lawrence ◽  
Clive R. Barlow ◽  
Keith Bensusan ◽  
Charles Perez ◽  
Stephen G. Willis
Keyword(s):  
Migratory Birds ◽  
Long Distance ◽  
Breeding Migration

scholarly journals Defining catchment origins of a geographical bottleneck: Implications of population mixing and phenological overlap for the conservation of Neotropical migratory birds

The Condor ◽  
2020 ◽  
Vol 122 (2) ◽  
Author(s):  
Laura Cardenas-Ortiz ◽  
Nicholas J Bayly ◽  
Kevin J Kardynal ◽  
Keith A Hobson
Keyword(s):  
Migratory Birds ◽  
Geographical Area ◽  
Weather Conditions ◽  
Neotropical Migrants ◽  
Long Distance ◽  
Catharus Ustulatus ◽  
Yellow Warbler ◽  
Population Mixing ◽  
Temporal Segregation ◽  
Adverse Weather

Abstract Migratory bottlenecks concentrate individuals and populations of Nearctic–Neotropical migrants from across vast breeding areas. The extent to which such concentrations occur has important ramifications for interpreting migratory connectivity and for the vulnerability of populations throughout the annual cycle but investigations of such phenomena are rare. We inferred breeding origins of 11 species of Nearctic–Neotropical migrants captured during fall migration in the Darién region, northwestern Colombia, using feather stable-hydrogen isotope values (δ 2Hf). Our objectives were to determine (1) the extent to which this region acts as a catchment for individuals from across a species’ breeding range, (2) if temporal patterns of arrival arise as a function of migration distance inferred from δ 2Hf, and (3) if phenological differences among species segregate populations. The Darién concentrated populations of 6 species, with individuals potentially derived from 78% to 94% of their respective North American breeding ranges. The catchment area for the remaining 5 species covered 40–72% of breeding ranges, with a bias in origin from the west (e.g., Northern Waterthrush [Parkesia noveboracensis], Swainson’s Thrush [Catharus ustulatus]), north or center (Yellow Warbler [Setophaga petechia]) of their range. Differential timing in the migration of populations occurred in 6 species, generating a degree of temporal segregation. In contrast, peak migration for all species occurred in October, resulting in high overlap among species in their use of the Darién. Overall, our results describe high mixing of populations in the Darién for several species, which, given the region’s highly restricted geographic extent, suggests that a bottleneck effect occurs; however, comparisons with other regions in Central America and northern South America are required. The combination of extensive population mixing and limited temporal segregation over a narrow geographical area suggests that long-distance migrants may be especially vulnerable to events occurring in such regions, including adverse weather conditions and anthropogenic land cover change.

scholarly journals Weather in The Breeding Area and During Migration Affects the Demography of a Small Long-Distance Passerine Migrant

The Auk ◽  
2005 ◽  
Vol 122 (2) ◽  
pp. 637-647 ◽  
Author(s):  
Bård G. Stokke ◽  
Anders Pape Møller ◽  
Bernt-Erik Sæther ◽  
Goetz Rheinwald ◽  
Hans Gutscher
Keyword(s):  
Population Size ◽  
Migratory Birds ◽  
Significant Proportion ◽  
Weather Conditions ◽  
Autumn Migration ◽  
Breeding Area ◽  
Long Distance ◽  
Apparent Survival ◽  
Negative Effect ◽  
Common House

Abstract Migratory birds are subject to the effects of various weather systems during the year. Fluctuations in population size may depend on survivorship of juveniles and adults at various stages of the annual cycle. Severe weather conditions can lower survival, especially in migrating passerines that feed on insects. We investigated the effects of climate and density dependence on survival in a population of Common House-Martins (Delichon urbicum), including variables of weather experienced both in their breeding areas and during autumn migration. Unfavorable weather conditions during autumn migration had a severe negative effect on adult apparent survival, irrespective of sex; whereas temperature in the breeding area and population size explained a significant proportion of variance in juvenile survival. Thus, weather conditions experienced in different areas can regulate various age classes in different ways, which suggests that climate change can have a significant but complex influence on demography in passerine populations.

scholarly journals Temperature change is an important departure cue in nocturnal migrants: controlled experiments with wild-caught birds in a proof-of-concept study

2020 ◽  
Vol 287 (1936) ◽  
pp. 20201650
Author(s):  
Thomas Klinner ◽  
Heiko Schmaljohann
Keyword(s):  
Climate Change ◽  
Decision Making ◽  
Migratory Birds ◽  
Global Climate ◽  
Decision Making Process ◽  
Proof Of Concept ◽  
Long Distance ◽  
Extrinsic Factors ◽  
Concept Study ◽  
Departure Probability

The decision-making process of migrating birds at stopover sites is a complex interplay of the innate migration program and both intrinsic and extrinsic factors. While it is well studied how variation in precipitation, wind and air pressure influence this process, there is less evidence of the effects of temperature changes on the departure decision. Thus, we lack knowledge on how the predicted changes due to global climate change in temperature alone may affect the decision-making process during migration. Aiming to fill parts of this gap, we conducted a proof-of-concept study by manipulating the ambient temperature of temporarily confined wild-caught migrant songbirds under constant feeding conditions. In spring, departure probability increased with a 20°C rise in temperature for both a medium-distance migrant (European robin, Erithacus rubecula ) and a long-distance migrant (northern wheatear, Oenanthe oenanthe ), and in autumn, departure probabilities of the long-distance migrant both decreased with a 20°C rise and increased with a 20°C drop. Consequently, the temperature is an important departure cue influencing the decision-making process of migrating songbirds. Incorporating causal relationships between changes in temperature and departure probability in migration models could substantially improve our ability to predict the effects of climate change on the phenology of migratory birds.

Electric Vehicle Charger Placement Optimization in Michigan Considering Monthly Traffic Demand and Battery Performance Variations

2021 ◽  
pp. 036119812098195
Author(s):  
Fatemeh Fakhrmoosavi ◽  
MohammadReza Kavianipour ◽  
MohammadHossein (Sam) Shojaei ◽  
Ali Zockaie ◽  
Mehrnaz Ghamami ◽  
...  
Keyword(s):  
Optimal Allocation ◽  
Critical Factor ◽  
Cold Weather ◽  
Contributing Factors ◽  
Modeling Framework ◽  
Long Distance ◽  
Charging Infrastructure ◽  
Traffic Demand ◽  
Adverse Weather ◽  
Performance Variations

Limited charging infrastructure for electric vehicles (EVs) is one of the main barriers to adoption of these vehicles. In conjunction with limited battery range, the lack of charging infrastructure leads to range-anxiety, which may discourage many potential users. This problem is especially important for long-distance or intercity trips. Monthly traffic patterns and battery performance variations are two main contributing factors in defining the infrastructure needs of EV users, particularly in states with adverse weather conditions. Knowing this, the current study focuses on Michigan and its future needs to support the intercity trips of EVs across the state in two target years of 2020 and 2030, considering monthly traffic demand and battery performance variations. This study incorporates a recently developed modeling framework to suggest the optimal locations of fast EV chargers to be implemented in Michigan. Considering demand and battery performance variations is the major contribution of the current study to the proposed modeling framework by the same authors in the literature. Furthermore, many stakeholders in Michigan are engaged to estimate the input parameters. Therefore, the research study can be used by authorities as an applied model for optimal allocation of resources to place EV fast chargers. The results show that for charger placement, the reduced battery performance in cold weather is a more critical factor than the increased demand in warm seasons. To support foreseeable annual EV trips in Michigan in 2030, this study suggests 36 charging stations with 490 chargers and an investment cost of $23 million.

Hierarchical Concept-Driven Language Model

2021 ◽  
Vol 15 (6) ◽  
pp. 1-22
Author(s):  
Yashen Wang ◽  
Huanhuan Zhang ◽  
Zhirun Liu ◽  
Qiang Zhou
Keyword(s):  
Language Model ◽  
Generation Process ◽  
Data Generation ◽  
Modeling Framework ◽  
Long Distance ◽  
Short Text ◽  
Proposed Model ◽  
Scalable Inference ◽  
End To End ◽  
Hidden Layer

For guiding natural language generation, many semantic-driven methods have been proposed. While clearly improving the performance of the end-to-end training task, these existing semantic-driven methods still have clear limitations: for example, (i) they only utilize shallow semantic signals (e.g., from topic models) with only a single stochastic hidden layer in their data generation process, which suffer easily from noise (especially adapted for short-text etc.) and lack of interpretation; (ii) they ignore the sentence order and document context, as they treat each document as a bag of sentences, and fail to capture the long-distance dependencies and global semantic meaning of a document. To overcome these problems, we propose a novel semantic-driven language modeling framework, which is a method to learn a Hierarchical Language Model and a Recurrent Conceptualization-enhanced Gamma Belief Network, simultaneously. For scalable inference, we develop the auto-encoding Variational Recurrent Inference, allowing efficient end-to-end training and simultaneously capturing global semantics from a text corpus. Especially, this article introduces concept information derived from high-quality lexical knowledge graph Probase, which leverages strong interpretability and anti-nose capability for the proposed model. Moreover, the proposed model captures not only intra-sentence word dependencies, but also temporal transitions between sentences and inter-sentence concept dependence. Experiments conducted on several NLP tasks validate the superiority of the proposed approach, which could effectively infer meaningful hierarchical concept structure of document and hierarchical multi-scale structures of sequences, even compared with latest state-of-the-art Transformer-based models.

scholarly journals Great flights by great snipes: long and fast non-stop migration over benign habitats

2011 ◽  
Vol 7 (6) ◽  
pp. 833-835 ◽  
Author(s):  
Raymond H. G. Klaassen ◽  
Thomas Alerstam ◽  
Peter Carlsson ◽  
James W. Fox ◽  
Åke Lindström
Keyword(s):  
Migratory Birds ◽  
Strenuous Exercise ◽  
Migration Route ◽  
Long Distance ◽  
Migration Strategy ◽  
Ice Caps ◽  
Fuel Loads ◽  
Stopover Sites ◽  
Ecological Barriers ◽  
Suitable Habitats

Migratory land birds perform extreme endurance flights when crossing ecological barriers, such as deserts, oceans and ice-caps. When travelling over benign areas, birds are expected to migrate by shorter flight steps, since carrying the heavy fuel loads needed for long non-stop flights comes at considerable cost. Here, we show that great snipes Gallinago media made long and fast non-stop flights (4300–6800 km in 48–96 h), not only over deserts and seas but also over wide areas of suitable habitats, which represents a previously unknown migration strategy among land birds. Furthermore, the great snipes achieved very high ground speeds (15–27 m s −1 ), which was not an effect of strong tailwind support, and we know of no other animal that travels this rapidly over such a long distance. Our results demonstrate that some migratory birds are prepared to accept extreme costs of strenuous exercise and large fuel loads, even when stopover sites are available along the route and there is little tailwind assistance. A strategy of storing a lot of energy before departure, even if migration is over benign habitats, may be advantageous owing to differential conditions of fuel deposition, predation or infection risk along the migration route.

scholarly journals Controlling Shipping Along the North European Trade Axis

1971 ◽  
Vol 24 (4) ◽  
pp. 553-556
Author(s):  
D. J. Lindsay
Keyword(s):  
Weather Conditions ◽  
North Coast ◽  
Baltic Basin ◽  
Long Distance ◽  
The North ◽  
Large Numbers ◽  
Straight Line ◽  
European Trade ◽  
Trade Route ◽  
The Baltic

By the North European Trade Axis is meant the trade route from Ushant and Land's End, up the English Channel, through the Dover Strait fanning out to serve eastern England, the north coast of continental Europe and leading to the Baltic Basin. Recent events in this area have left a feeling that some form of tightening of control is not only desirable, but is rapidly becoming imperative. There is a basic conflict between the two forms of shipping using the area: the local users who use the area more or less constantly, and the long-distance traders, usually much larger, which arrive in the area for a brief stay after a prolonged period at sea, which has usually been in good weather conditions. Frequently these latter ships have a very poor notion of the hornet's nest into which they are steaming when they arrive. The net result is all too often the same: the local users, with familiarity breeding contempt, wander about as they see fit, with scant regard for routing or the regulations; all too often the big ships arrive from sea with navigating staffs who are too confused, sometimes too ignorant—and sometimes too terrified—to do much more than blunder forward in a straight line hoping for the best. Quite obviously this is not a total picture, and there are large numbers of ships which navigate perfectly competently, but the minority of those which do not seem to be rising rapidly, and show every sign of continuing to increase.

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