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Automatic classification of animal vocalizations has great potential to enhance the monitoring of species movements and behaviors. This is particularly true for monitoring nocturnal bird migration, where automated classification of migrants' flight calls could yield new biological insights and conservation applications for birds that vocalize during migration. In this paper we investigate the automatic classification of bird species from flight calls, and in particular the relationship between two different problem formulations commonly found in the literature: classifying a short clip containing one of a fixed set of known species (N-class problem) and the continuous monitoring problem, the latter of which is relevant to migration monitoring. We implemented a state-of-the-art audio classification model based on unsupervised feature learning and evaluated it on three novel datasets, one for studying the N-class problem including over 5000 flight calls from 43 different species, and two realistic datasets for studying the monitoring scenario comprising hundreds of thousands of audio clips that were compiled by means of remote acoustic sensors deployed in the field during two migration seasons. We show that the model achieves high accuracy when classifying a clip to one of N known species, even for a large number of species. In contrast, the model does not perform as well in the continuous monitoring case. Through a detailed error analysis (that included full expert review of false positives and negatives) we show the model is confounded by varying background noise conditions and previously unseen vocalizations. We also show that the model needs to be parameterized and benchmarked differently for the continuous monitoring scenario. Finally, we show that despite the reduced performance, given the right conditions the model can still characterize the migration pattern of a specific species. The paper concludes with directions for future research.

What do a bumble bee and a 747 jet have in common? It's not a trick question. The fact is they have quite a lot in common. They both have wings. They both fly. And they're both ideally suited to it. They just do it differently.Why Don't Jumbo Jets Flap Their Wings? offers a fascinating explanation of how nature and human engineers each arrived at powered flight. What emerges is a highly readable account of two very different approaches to solving the same fundamental problems of moving through the air, including lift, thrust, turning, and landing. The book traces the slow and deliberate evolutionary process of animal flight-in birds, bats, and insects-over millions of years and compares it to the directed efforts of human beings to create the aircraft over the course of a single century.Among the many questions the book answers:Why are wings necessary for flight?How do different wings fly differently?When did flight evolve in animals?What vision, knowledge, and technology was needed before humans could learn to fly?Why are animals and aircrafts perfectly suited to the kind of flying they do?David E. Alexander first describes the basic properties of wings before launching into the diverse challenges of flight and the concepts of flight aerodynamics and control to present an integrated view that shows both why birds have historically had little influence on aeronautical engineering and exciting new areas of technology where engineers are successfully borrowing ideas from animals.

Musculoskeletal systems cope with many environmental perturbations without neurological control. These passive preflex responses aid animals to move swiftly through complex terrain. Whether preflexes play a substantial role in animal flight is uncertain. We investigated how birds cope with gusty environments and found that their wings can act as a suspension system, reducing the effects of vertical gusts by elevating rapidly about the shoulder. This preflex mechanism rejected the gust impulse through inertial effects, diminishing the predicted impulse to the torso and head by 32% over the first 80 ms, before aerodynamic mechanisms took effect. For each wing, the centre of aerodynamic loading aligns with the centre of percussion, consistent with enhancing passive inertial gust rejection. The reduced motion of the torso in demanding conditions simplifies crucial tasks, such as landing, prey capture and visual tracking. Implementing a similar preflex mechanism in future small-scale aircraft will help to mitigate the effects of gusts and turbulence without added computational burden.

No detailed description available for \"The Inner Bird\".

The most comprehensive account of the origin of ancient and modern birds—the \"living dinosaurs.\" A small set of fossilized bones discovered almost thirty years ago led paleontologist Sankar Chatterjee on a lifelong quest to understand their place in our understanding of the history of life. They were clearly the bones of something unusual, a bird-like creature that lived long, long ago in the age of dinosaurs. He called it Protoavis, and the animal that owned these bones quickly became a contender for the title of \"oldest known bird.\" In 1997, Chatterjee published his findings in the first edition of The Rise of Birds. Since then Chatterjee and his colleagues have searched the world for more transitional bird fossils. And they have found them. This second edition of The Rise of Birds brings together a treasure trove of fossils that tell us far more about the evolution of birds than we once dreamed possible. With no blind allegiance to what he once thought he knew, Chatterjee devours the new evidence and lays out the most compelling version of the birth and evolution of the avian form ever attempted. He takes us from Texas to Spain, China, Mongolia, Madagascar, Australia, Antarctica, and Argentina. He shows how, in the \"Cretaceous Pompeii\" of China, he was able to reconstruct the origin and evolution of flight of early birds from the feathered dinosaurs that lay among thousands of other amazing fossils. Chatterjee takes us to where long-hidden bird fossils dwell. His compelling, occasionally controversial, revelations—accompanied by spectacular illustrations—are a must-read for anyone with a serious interest in the evolution of \"the feathered dinosaurs,\" from vertebrate paleontologists and ornithologists to naturalists and birders.

Wind power, as a critical source of renewable energy to combat global warming, is growing rapidly worldwide. A great concern has arisen over the killing of a great number of birds by wind turbines. There has been much research on this issue based on observational and statistical data. However, it remains unknown how the wind turbine wakes affect the bird flight from a fluid dynamic and mechanical perspective. The wind turbine wakes calculated by the large eddy simulation are used as boundary input to simulate the flying of bird. A number of 62 bird flight simulations are run to calculate the lift-to-drag ratio, and then fitted to get its distribution over the whole wake area. Results reveal bird flights are affected most near the upper blade tip, with a maximum reduction in lift-to-drag ratio of about 30%. Conversely, turbine wakes below bottom tip level assist bird flight, suggesting a potential low-altitude route through wind farms. Wake superposition exacerbates adverse aerodynamic effects, and a staggered layout strategy can reduce the negative impact. The findings will benefit the conservation of birds and assist the sustainable development of wind farms.

Background Over the past decade, the miniaturisation of animal borne tags such as geolocators and GPS-transmitters has revolutionized our knowledge of the whereabouts of migratory species. Novel light-weight multi-sensor loggers (1.4 g), which harbour sensors for measuring ambient light intensity, atmospheric pressure, temperature and acceleration, were fixed to two long-distance migrant bird species - eurasian hoopoe ( Upupa epops ) and great reed warbler ( Acrocephalus arundinaceus ). Using acceleration and atmospheric pressure data recorded every 5 and 30 min, respectively, we aimed at reconstructing individual diurnal and seasonal patterns of flight activity and flight altitude and thereby, at describing basic, yet hitherto unknown characteristics of migratory flight behaviour. Furthermore, we wanted to characterise the variability in these migration characteristics between individuals, species and migration periods. Results The flight duration from breeding to sub-Saharan African non-breeding sites and back was more variable within than between the species. Great reed warblers were airborne for a total of 252 flight hours and thus, only slightly longer than eurasian hoopoes with 232 h. With a few exceptions, both species migrated predominantly nocturnally - departure around dusk and landing before dawn. Mean flight altitudes were higher during pre- than during post-breeding migration (median 1100 to 1600 m a.s.l.) and flight above 3000 m occurred regularly with a few great reed warblers exceeding 6000 m a.s.l. (max. 6458 m a.s.l.). Individuals changed flight altitudes repeatedly during a flight bout, indicating a continuous search for (more) favourable flight conditions. Conclusions We found high variation between individuals in the flight behaviour parameters measured – a variation that surprisingly even exceeded the variation between the species. More importantly, our results have shown that multi-sensor loggers have the potential to provide detailed insights into many fundamental aspects of individual behaviour in small aerial migrants. Combining the data recorded on the multiple sensors with, e.g., remote sensing data like weather and habitat quality on the spatial and temporal scale will be a great step forward to explore individual decisions during migration and their consequences.

Migration is a common trait among many animals allowing the exploitation of spatiotemporally variable resources. It often implies high energetic costs to cover large distances, for example between breeding and wintering grounds. For flying or swimming animals, the adequate use of winds and currents can help reduce the associated energetic costs. Migratory seabirds are good models because they dwell in habitats characterized by strong winds while undertaking very long migrations. We tested the hypothesis that seabirds migrate through areas with favourable winds. To that end, we used the SEATRACK dataset, a multi‐colony geolocator tracking dataset, for two North Atlantic seabirds with contrasting flight capabilities, the black‐legged kittiwake Rissa tridactyla and the Atlantic puffin Fratercula arctica , and wind data from the ERA5 climate reanalysis model. Both species had on average positive wind support during migration. Their main migratory routes were similar and followed seasonally prevailing winds. The general migratory movement had a loop‐shape at the scale of the North Atlantic, with an autumn route (southward) along the east coast of Greenland, and a spring route (northward) closer to the British Isles. While migrating, both species had higher wind support in spring than in autumn. Kittiwakes migrated farther and benefited from higher wind support than puffins on average. The variation in wind conditions encountered while migrating was linked to the geographical location of the colonies. Generally, northernmost colonies had a better wind support in autumn while the southernmost colonies had a better wind support in spring, with some exceptions. Our study helps understanding how the physical environment shapes animal migration, which is crucial to further predict how migrants will be impacted by ongoing environmental changes.

Flapping flight places strenuous requirements on the physiological performance of an animal. Bird flight muscles, particularly at smaller body sizes, generally contract at high frequencies and do substantial work in order to produce the aerodynamic power needed to support the animal's weight in the air and to overcome drag. This is in contrast to terrestrial locomotion, which offers mechanisms for minimizing energy losses associated with body movement combined with elastic energy savings to reduce the skeletal muscles' work requirements. Muscles also produce substantial power during swimming, but this is mainly to overcome body drag rather than to support the animal's weight. Here, I review the function and architecture of key flight muscles related to how these muscles contribute to producing the power required for flapping flight, how the muscles are recruited to control wing motion and how they are used in manoeuvring. An emergent property of the primary flight muscles, consistent with their need to produce considerable work by moving the wings through large excursions during each wing stroke, is that the pectoralis and supracoracoideus muscles shorten over a large fraction of their resting fibre length (33–42%). Both muscles are activated while being lengthened or undergoing nearly isometric force development, enhancing the work they perform during subsequent shortening. Two smaller muscles, the triceps and biceps, operate over a smaller range of contractile strains (12–23%), reflecting their role in controlling wing shape through elbow flexion and extension. Remarkably, pigeons adjust their wing stroke plane mainly via changes in whole-body pitch during take-off and landing, relative to level flight, allowing their wing muscles to operate with little change in activation timing, strain magnitude and pattern.