Birds Fly Research Articles

Bird movements at rotor heights measured continuously with vertical radar at a Dutch offshore wind farm

Assessing the impacts of avian collisions with wind turbines requires reliable estimates of avian flight intensities and altitudes, to enable accurate estimation of collision rates, avoidance rates and related effects on populations. At sea, obtaining such estimates visually is limited not only by weather conditions but, more importantly, because a high proportion of birds fly at night and at heights above the range of visual observation. We used vertical radar with automated bird‐tracking software to overcome these limitations and obtain data on the magnitude, timing and altitude of local bird movements and seasonal migration measured continuously at a Dutch offshore wind farm. An estimated 1.6 million radar echoes representing individual birds or flocks were recorded crossing the wind farm annually at altitudes between 25 and 115 m (the rotor‐swept zone). The majority of these fluxes consisted of gull species during the day and migrating passerines at night. We demonstrate daily, monthly and seasonal patterns in fluxes at rotor heights and the influence of wind direction on flight intensity. These data are among the first to show the magnitude and variation of low‐altitude flight activity across the North Sea, and are valuable for assessing the consequences of developments such as offshore wind farms for birds.

Extreme variation in migration strategies between and within wandering albatross populations during their sabbatical year, and their fitness consequences.

Migratory behavior, routes and zones used during the non-breeding season are assumed to have been selected to maximize fitness, and can lead to genetic differentiation. Yet, here we show that migration strategies differ markedly between and within two genetically similar populations of wandering albatross Diomedea exulans from the Crozet and Kerguelen archipelagos in the Indian Ocean. Wandering albatrosses usually breed biennially if successful, and during the sabbatical year, all birds from Kerguelen migrate to the Pacific Ocean, whereas most from Crozet are sedentary. Instead of taking the shortest routes, which would involve a return against headwinds, migratory birds fly with the westerly winds, requiring detours of 10,000 s km. In total, migrants circumnavigate Antarctica 2 to 3 times, covering more than 120,000 km in a single sabbatical year. Our results indicate strong links between migratory behavior and fitness; all birds from Kerguelen breed biennially, whereas a significant proportion of those from Crozet, especially females, are sedentary and breed in consecutive calendar years. To breed annually, these females temporarily change mate, but return to their original partner in the following year. This extreme variation in migratory behavior has important consequences in term of life history evolution and susceptibility to climate change and fisheries.

Magpies Waiting for Redevelopment, and: Lyrics, Too, Have Class Structures, and: Winter That Year at Dotgot, and: Beyond the Border, and: Love Song for Garibong Five-way Crossing, and: Being Shadowed

Magpies Waiting for Redevelopment, and: Lyrics, Too, Have Class Structures, and: Winter That Year at Dotgot, and: Beyond the Border, and: Love Song for Garibong Five-way Crossing, and: Being Shadowed Song Kyung-dong Translated by Chung Eun-Gwi (bio) and Brother Anthony of Taizé (bio) magpies waiting for redevelopment Having a pee in the fourth-floor washroom of a commercial building in Guro market, I see a magpie through the window, sitting on a telephone pole. Intending to build a nest, the bird holds a twig in its beak, testing one angle, then another. Like a careful carpenter it considers one factor and then another. The dried twig twists precariously in the wind, as if saying: Not here. Securing the twig in its beak, the bird flies on through the forest of concrete apartments. Ah, bird! Why is it so difficult for us to find a house— even one in the sky? lyrics, too, have class structures Once I thought my chest held a garden larger than a laborer’s lodging. I thought of it as brighter than a room at a pub, calmer than a workshop throbbing with the sound of generators. [End Page 29] Carpenters, painters, laborers, lowlife, lower life, I welcomed them all inside me. Living with those rootless lives inside my own breast, I was excited as the owner of a room for rent. However, looking back after many years, I see I spoiled that place of an endless spring of lyrics singing by filling it with difficult books, science, and reason. When tipsy sunset lay sprawled across golden meadows, unable to stand, and nobody woke him those warm summer days— ah, my poor lyrics! winter that year at dotgot In the winter of that year, I buried love at Dotgot. As a cold, rusty wind came blowing over the dyke of the reclaimed land, I clung tightly to a steel I-beam like a ledge of ice tens of meters in the air, crawled on all fours to keep from falling to my death, and buried your memory. Huddling around a bonfire eating frigid snacks, stomping loudly up iron stairs, making a racket for no reason. I saw my fellow workers lose limbs crushed by steel girders, lose eyes to grinder blades, and fall from great heights, and it banished, from deep inside me, the longing for your body. On days off, I would hang out in poolrooms near the construction site or sit in a coffee shop in a far-off town, searching for traces of you. When we met, I was a poor apprentice welder and you were a penniless café waitress. I wonder where we lost the sweet love that we had. I hammered full of fury the hot welding rod that splintered flames in my heart . . . When night fell over the 500-acre worksite of reclaimed land, the men would wait in line to use the canteen’s single phone booth, shaking the coins in their pockets and shivering in the cold. [End Page 30] But because I didn’t have the heart to call you I would wear myself out walking to the distant wharf, then return iced over like a snowman. Men were laid off, wages were cut. In the dorms, the workers began to whisper: We should stage a slowdown, go out on strike. But such actions were futile. As I stood at the iron railing, twenty stories high, calling your name, how far my voice carried I don’t know. Where did we lose the innocent love we had? beyond the border I am not my own thing. Today I ate rice from Pyongtaek, garlic from Seosan, grapes from Yeon-dong, tofu made in China, and mackerel from Chile. My bones, flesh, blood, organs, and thoughts in fact have their roots in different places. It is morally wrong for me, being such a borderless thing, to be obsessed with a single idea. It’s also unreasonable to insist that change must happen only in a certain way. Harsh like sunlight, then cool like mist, then piled up like mountains, then endlessly expansive like the sea, like plains, every manner of being is inside me. Thinking that...

猫头鹰的静音飞行机理研究

猫头鹰在所有鸟类中飞行噪声最低，这一现象引起了鸟类学家、声学专家甚至军事专家的极大兴趣。本文首先测试了猫头鹰的飞行噪声特性，进而对猫头鹰翅膀翼型的宏观形态特征以及气动和声学特性，猫头鹰体表羽毛的微观结构特征和力学特性，猫头鹰体表皮肤和皮下结构的微观结构特征及其吸声特性开展了较为系统的研究，发现猫头鹰独特的静音飞行能力实际上是源于多个降噪因素综合产生的总体效应，是消声降噪和吸声降噪两种机制的共同作用，这对于研究减振降噪技术有着极为重要的启发意义和参考价值。 The silent flight of owls has long fascinated ornithologists, acoustic specialists, and even military experts; no other birds fly with such distinct advantages. In this work, the flight noise of a bubo bubo (a kind of large owl) was recorded, and followed by a comprehensive study on the mechanism of the silent flight, including research on the wing profile and its aerodynamic performance and acoustic property, the morphology of the feathers and its mechanical characteristics, as well as the microscopic structure of the skin and its sound absorption performance. It is concluded that the unique ability of silent flight of owls attributes to the combination of multiple noise reduction factors, sorted as sound suppression and sound absorption, which has piqued the interest of biomimetic research for noise control.

Fluid structures of flapping airfoil with elliptical motion trajectory

In the present study, the effect of elliptical motion trajectory on the aerodynamic characteristics and propulsive performance of a flapping airfoil is evaluated. A periodic horizontal motion (forward/backward) is combined with vertical motion (upward/downward) of the airfoil to introduce a new kinematic parameter, and of course, an elliptical motion trajectory for flapping airfoil. Similar kinematics is also observed in the flying of birds and swimming of the penguins or turtles. For this modeling, the Navier–Stokes equations are used to simulate the unsteady flow field over a two dimensional NACA0012 airfoil. The Navier–Stokes equations are discretized based on the finite volume method and are solved with a pressure-based algorithm. The flow is assumed to be laminar and incompressible and transient terms are conducted using a second order Euler implicit scheme. It is shown that the combination of horizontal and vertical motions for the flapping airfoil changes the kinematics, motion trajectory and hence the effective angle of attack profile during the flapping cycle. The elliptical motion trajectory will also influence on the fluid structures and change the vortex shedding pattern and wake zone behind the airfoil. Additionally, the introduced kinematics may influence significantly on the aerodynamics and propulsive performance of either pure plunging or pitching/plunging airfoil.

The Dictator Declares War

The Dictator Declares War Jeannie Vanasco (bio) He closes his eyes and spins his globe. His finger lands on water. He spins again.More water.The Enemy is in the ocean, he warns his citizens.His military ships fire torpedoes at nothing. Nothing fires back.The nation must fight something, his advisors tell him.So the dictator spins his globe until his finger lands on his land.The Enemy is in our midst, he warns his citizens.He sends lawyers to his generals. The lawyers advise who can and cannot be killed.Innocent civilians can be killed, provided sections 1, 4, 19, 23, 423 (see clauses 194, 3, 17, 348, 421, respectively).Peaceful protestors can be killed, provided sections 2, 9, and 41 (see clauses 5, 2, and 9, respectively).Birds can be killed, provided section 132, clause 956.The legal documents grow as big as tanks.Extinct birds fly underground. [End Page 61] Jeannie Vanasco Jeannie Vanasco is writing a book involving necronyms, mental illness, and an artificial eye. Her writing has appeared in the Believer, Times Literary Supplement, Tin House, and elsewhere. Copyright © 2014 University of Nebraska Press

Minding the gap: in-flight body awareness in birds

When birds fly in cluttered environments, they must tailor their flight to the gaps that they traverse. We trained budgerigars, Melopsittacus undulatus, to fly through a vertically oriented gap of variable width, to investigate their ability to perform evasive manoeuvres during passage. When the gap was wider than their wingspan, the birds passed through it without interrupting their flight. When traversing narrower gaps, however, the birds interrupted their normal flight by raising their wings or tucking them against the body, to prevent contact with the flanking panels. Our results suggest that the birds are capable of estimating the width of the gap in relation to their wingspan with high precision: a mere 6% reduction in gap width causes a complete transition from normal flight to interrupted flight. Furthermore, birds with shorter wingspans display this transition at narrower gap widths. We conclude from our experiments that the birds are highly aware of their individual body size and use precise, anticipatory, visually based judgements to control their flight in complex environments.

Role of projection in the control of bird flocks.

Swarming is a conspicuous behavioral trait observed in bird flocks, fish shoals, insect swarms, and mammal herds. It is thought to improve collective awareness and offer protection from predators. Many current models involve the hypothesis that information coordinating motion is exchanged among neighbors. We argue that such local interactions alone are insufficient to explain the organization of large flocks of birds and that the mechanism for the exchange of long-range information necessary to control their density remains unknown. We show that large flocks self-organize to the maximum density at which a typical individual still can see out of the flock in many directions. Such flocks are marginally opaque--an external observer also still can see a substantial fraction of sky through the flock. Although this seems intuitive, we show it need not be the case; flocks might easily be highly diffuse or entirely opaque. The emergence of marginal opacity strongly constrains how individuals interact with one another within large swarms. It also provides a mechanism for global interactions: an individual can respond to the projection of the flock that it sees. This provides for faster information transfer and hence rapid flock dynamics, another advantage over local models. From a behavioral perspective, it optimizes the information available to each bird while maintaining the protection of a dense, coherent flock.

Quantum causal explanation: or, why birds fly south

It is widely held that it is difficult, if not impossible, to apply causal theory to the domain of quantum mechanics. However, there are several recent scientific explanations that appeal crucially to quantum processes, and which are most naturally construed as causal explanations. They come from two relatively new fields: quantum biology and quantum technology. We focus on two examples, the explanation for the optical interferometer LIGO and the explanation for the avian magneto-compass. We analyse the explanation for the avian magneto-compass from the perspective of Woodward's interventionist theory and provide a causal model. Furthermore, we show how worries expressed by Woodward about quantum causation are circumvented in these cases, concluding that these kinds of explanations are most naturally construed as causal.

The Long, Long Line by T. Ohmura

Ohmura, Tomoko. The Long, Long Line. Toronto, ON: OwlKids Books, 2013. Print."Thank you for waiting, and welcome aboard! One at a time, please!" mentions the bird, who is the ride guide on this mysterious ride for which 50 different animals have patiently lined up. As they wait, the bird flies amongst them, offering reassuring words as they guess as to what they may be in line for and play word games to pass the time. The anticipation builds, and finally they start boarding the ride, which turns out to be a very large whale on which the animals ride while the whale performs somersaults, dives and sprays. Children will be delighted by all 50 animals represented on the large gatefold spread in the center of the book, from the smallest frog to the largest elephant.Children will love the small details such as the tail of the next animal in line ‘peeking’ around the corner of the page and the size of the animals increasing as they get closer to the ride giving perspective of size. A list of all 50 animals is included at the back for easy reference when young readers get stumped by a species. While this is indeed a picture book aimed at young children it is no quick read – children will want to hear every word of the animals’ conversations as they wait and will want to count as they go, and likely once all the animals are aboard the whale they will want to confirm there are indeed 50 animals present, perhaps multiple times.The colourful illustrations by the author are cute and engaging and show a wide range of expressions and interplay between the animals. The language felt slightly unnatural but this may be a result of this edition being a translation of the original Japanese work Nanno Gyoretsu? A fun book for public and elementary schools as well as a nice addition to science or math based storytime in lower elementary grades.The Long, Long Line was selected as one of the best children’s books of 2013 by Kirkus Reviews.Recommended: 3 out of 4 stars Reviewer: Debbie FeisstDebbie is a Public Services Librarian at the H.T. Coutts Education Library at the University of Alberta. When not renovating, she enjoys travel, fitness and young adult fiction.

Upwash exploitation and downwash avoidance by flap phasing in ibis formation flight

Many species travel in highly organized groups. The most quoted function of these configurations is to reduce energy expenditure and enhance locomotor performance of individuals in the assemblage. The distinctive V formation of bird flocks has long intrigued researchers and continues to attract both scientific and popular attention. The well-held belief is that such aggregations give an energetic benefit for those birds that are flying behind and to one side of another bird through using the regions of upwash generated by the wings of the preceding bird, although a definitive account of the aerodynamic implications of these formations has remained elusive. Here we show that individuals of northern bald ibises (Geronticus eremita) flying in a V flock position themselves in aerodynamically optimum positions, in that they agree with theoretical aerodynamic predictions. Furthermore, we demonstrate that birds show wingtip path coherence when flying in V positions, flapping spatially in phase and thus enabling upwash capture to be maximized throughout the entire flap cycle. In contrast, when birds fly immediately behind another bird--in a streamwise position--there is no wingtip path coherence; the wing-beats are in spatial anti-phase. This could potentially reduce the adverse effects of downwash for the following bird. These aerodynamic accomplishments were previously not thought possible for birds because of the complex flight dynamics and sensory feedback that would be required to perform such a feat. We conclude that the intricate mechanisms involved in V formation flight indicate awareness of the spatial wake structures of nearby flock-mates, and remarkable ability either to sense or predict it. We suggest that birds in V formation have phasing strategies to cope with the dynamic wakes produced by flapping wings.

Taking a Joke Seriously: Mickey Mouse and William Kentridge

Taking a Joke Seriously:Mickey Mouse and William Kentridge1 Nienke Boer Transformation, metamorphosis is of course the bread and butter of animation in the studio. Something difficult to do… on the stage, to turn a cat into a telephone, gets called together by the cloth, the paper, the charcoal, the eraser. —William Kentridge, "Drawing Lesson 5: In Praise of Mistranslation." The film opens in what appears to be the control room of a large organization: computers line the left wall, and, on a large clock, moving hands illustrate the passage of time. The scene shifts abruptly to a man in a pinstriped business suit, standing in what seems to be a bedroom (wood flooring, a fireplace, a small rug and the end of a single bed), reading a letter, which moves slightly as he holds it. Then, the third scene: a difficult-to-identify structure next to the side of a road—gleaming tracks on the road suggest that it could be a tram station, but the position of the windows also hint at the security booth of a gated community or large business. A bird flies over from the top left corner of the screen, leaving a smudged trail behind it, and the scene changes again, to a close-up of the top of [End Page 1146] a power line, where a bird (the same one?) appears at the top left corner and flies across the screen, still trailing black smudges. Finally, the scene shifts again and a black cat walks across the screen from left to right. As the cat walks along a white wall, letters spelling out the word "Stereoscope" appear one by one on the wall behind it. This is the "cold open" of William Kentridge's eighth Drawing for Projection, Stereoscope (1999). All of this is drawn in charcoal and animated by a kind of stop-motion animation, where small changes are made to a base drawing in between sequential shots of it. Thus "each sequence as opposed to each frame of the film is a single drawing" (Kentridge, "'Fortuna'" 64). The charcoal leaves smudged traces behind when it is erased, resulting in, for example, the trail behind the bird as it flies across the sky. Kentridge uses this technique, which he calls "stone age film-making" ("'Fortuna'" 61), to produce a drawn and animated world peopled by three main characters—the man in the pinstripe suit, Soho Eckstein, his wife, Mrs. Eckstein, and Felix Teitlebaum, an artist who pursues Mrs. Eckstein—along with an accompanying cast of, among others, miners, doctors, police agents, a land surveyor called Nandi, a living statue, and an omnipresent black cat. I've described this opening sequence in such great detail because it includes many of the stylistic features that I'll discuss in this paper: the imitation of filmic conventions (the moving hands on the clock indicating the accelerated passage of time); the use of visual cues to create meaning (we know Soho is reading the letter because it moves slightly in his hand); the creation of continuity between shots (the bird flying from left to right, linking two sequential drawings, suggests that these scenes are temporally and geographically adjacent); the mixing of realistic and impossible effects (the outsize cat patrolling a suburban wall and producing the word "Stereoscope" behind it). In my attempt to address the question of why Kentridge, in this particular section of his substantial body of work (which includes everything from constructing large mechanically-operated music instruments to directing and co-designing the Metropolitan Opera's 2010 production of Shostakovich's The Nose), chooses to engage with animation, I examine how he uses both the technological apparatus and techniques of this medium, and what they allow him to do. In this brief introduction I begin to suggest some answers, but a fuller explanation will require me to delve back into the history of the medium itself. Rosalind Krauss, in her article "'The Rock': William Kentridge's Drawings for Projection" (originally published in 2000), has written very insightfully on Kentridge's technique of "stone-age film-making." To [End Page 1147] Krauss, "the medium is the memory" (19), and thus, in order to study...

The furcula and the evolution of avian flight

The presence of a short furcula in Archaeopteryx suggests that this bird possessed a small, shortfibered, cranial portion of the pinnate m. pectoralis originating from the furcula and possibly from the aponeurosis between the furcula and the coracoid and cartilaginous sternum, and inserting on the cranial edge of the humerus, and an equally small, short-fibered pinnate caudal part of the same muscle arising from the presumably cartilaginous sternum and inserting on the ventral surface of the deltoid crest of the humerus. In Archaeopteryx, the cranial-most portion of the m. pectoralis protracted the wing and held it in place against the backward pressure, or drag, of the air when the bird flew. There is no basis for postulating that the caudal part of the m. pectoralis in Archaeopteryx was sufficiently large for active flapping flight, although this presumably small muscle probably held the wings in a horizontal position necessary for aerial locomotion. The muscle fibers of all parts of the m. pectoralis were short because the small distance between its origin and insertion. The combination of features in the pectoral system of Archaeopteryx indicates strongly that this bird was a specialized glider, not an active flapping flier. Avian flight started from the trees downward, not from the ground upward.

Hinterland's Who’s Who: Birding, Multiplicity, and Barn Owls

Hinterland's Who’s Who: Birding, Multiplicity, and Barn Owls

BIRDS’ FLIGHT ENERGY PREDICTIONS AND APPLICATION TO RADAR-TRACKING STUDY

<p>In offered research, we propose to observe diurnal soaring birds to check, whether there the positions of birds in formations are such, that the wing tip interval and depth meet the predictions of aerodynamic theory for achievement of maximal conservation of energy or predictions of the hypothesis of communication. We also can estimate, whether adverse conditions of a wind influence the ability of birds to support formation. We can assume that windy conditions during flight might make precision flight more difficult by inducing both unpredictable bird and vortex positions. To this, we need to found change in wing-tip spacing variation with increasing wind speed, suggesting or rejecting that in high winds bird skeins maintained similar variation to that on calm days. The interrelation between variation of mean depth and wind speed should prove this hypothesis. Little is known about the importance of depth, but in high winds the vortex is likely to break up more rapidly and its location become unpredictable the further back a bird flies; therefore, a shift towards skeins with more regular depths at high wind speeds may compensate for the unpredictability of the vortex locations. Any significant relationship between the standard deviation of wing-tip spacing and wind speed suggests that wind has a major effect on optimal positioning.</p> <p>Results of proposed study will be used also as the auxiliary tool in radar research of bird migration, namely in research of flight features of soaring birds. It is extremely important to determine all pertinent characteristics of flock for model species, namely flocking birds.</p> <p><em>Kew words: birds, flock, radar, flight</em></p><p> </p>

If a bird flies in the forest, does an insect hear it?

Birds are major predators of many eared insects including moths, butterflies, crickets and cicadas. We provide evidence supporting the hypothesis that insect ears can function as 'bird detectors'. First, we show that birds produce flight sounds while foraging. Eastern phoebes (Sayornis phoebe) and chickadees (Poecile atricapillus) generate broadband sounds composed of distinct repetitive elements (approx. 18 and 20 Hz, respectively) that correspond to cyclic wing beating. We estimate that insects can detect an approaching bird from distances of at least 2.5 m, based on insect hearing thresholds and sound level measurements of bird flight. Second, we show that insects with both high and low frequency hearing can hear bird flight sounds. Auditory nerve cells of noctuid moths (Trichoplusia ni) and nymphalid butterflies (Morpho peleides) responded in a bursting pattern to playbacks of an attacking bird. This is the first study to demonstrate that foraging birds generate flight sound cues that are detectable by eared insects. Whether insects exploit these sound cues, and alternatively, if birds have evolved sound-reducing foraging tactics to render them acoustically 'cryptic' to their prey, are tantalizing questions worthy of further investigation.

Distribution, Phenology and Long-Term Population Trends in Blacktailed Godwits LimosaLimosa winteringin Coastal France

Species with known long-term changes in abundance and distribution enable exploring the role of newly accessible sites in population regulation. In Western Europe, the Black-tailed Godwit Limosa limosa islandica is one of the few wintering shorebirds with increasing populations. The French coasts comprise a major wintering site within its global wintering area, with several thousand individuals at some sites. Nevertheless, the role and importance of French sites in general distribution patterns of the species remain unclear, especially as its hunting was legal there until 2008. In contrast, recent increases in protected areas in France (from 4,000 ha in 1973 to 28,000 ha in 2005) offer new safe sites and suitable habitats for the species. In this study, we assessed the numbers and distribution of Black-tailed Godwits along the coasts of Western France. The main wintering sites in France are progressively occupied from August, reaching peak occupation in late autumn or early winter although few of the ten sites listed showed similar patterns of monthly variations in the distribution of Godwit numbers. France welcomes c. 28% of the total L. l. islandica population in mid-winter over the period 2003–2007. Numbers declined steadily from the base year (1977) until 1991, then progressively increased, reaching a maximum in 2010 (c. 27,000 individuals). The creation of Nature Reserves throughout the 1990s probably contributed to the increasing number of Godwits in France, with new accessible sites visited and occupied intensively during the period of population increase. The clearly contrasting phenologies between the British Isles and France suggest that most of the individuals first arrive in the United Kingdom after the breeding season, and then some of the birds move to southern sites in either France or Iberia, while very few birds fly directly to France from Iceland.

The use of hormonal therapy in “andropause”: the con side

The use of hormonal therapy in “andropause”: the con side

"A Bird Flying in Spiritual Sky between Love, Fear and Hope"

The widespread emergence of ethical failures in business has promoted interest in behavioural ethics. This emerging approach gives attention to individual actual behaviour to understand how to manage unethical behaviours in organisations. Ethics are clearly one aspect of modern business where the impact of religion has been shown to be significant. In this regard, many descriptive studies use a behavioural business ethics approach to examine the influence of religiosity on individual ethical behaviour in the workplace. However, the overwhelming majority of these studies linked Western Christianity to individual ethical behaviour while studies that focus on Islam are lacking. A critical reason behind this gap in the literature might be the necessity for comprehensive understanding of the Islamic faith and ethical system in order to identify and incorporate religious role expectations that constitute Muslim self-identity. Such a task is associated with difficulties as it engages the business researcher in the unfamiliar territory of Islamic theological and cultural literature in addition to the business ethics literature. This paper engages in such a task to provide a faith-based framework to be a solid foundation for empirical support within the realm of business. Moreover, it identifies potential future empirical research that would be facilitated by our conceptual framework. Keywords: Tawheed; Iman; ethical decision-making; Balanced view; Hope view; Fear view; Love view; Symbolic interactionist theory.

Generic language use reveals domain differences in young children's expectations about animal and artifact categories

The goal of the present study was to explore domain differences in young children's expectations about the structure of animal and artifact categories. We examined 5-year-olds’ and adults’ use of category-referring generic noun phrases (e.g., “Birds fly”) about novel animals and artifacts. The same stimuli served as both animals and artifacts; thus, stimuli were perceptually identical across domains, and domain was indicated exclusively by language. Results revealed systematic domain differences: children and adults produced more generic utterances when items were described as animals than artifacts. Because the stimuli were novel and lacking perceptual cues to domain, these findings must be attributed to higher-order expectations about animal and artifact categories. Overall, results indicate that by age 5, children are able to make knowledge-based domain distinctions between animals and artifacts that may be rooted in beliefs about the coherence and homogeneity of categories within these domains.