Optic Flow Cues Guide Flight in Birds Bhagavatula, Partha S.; Claudianos, Charles; Ibbotson, Michael R. ...
CB/Current biology,
11/2011, Volume:
21, Issue:
21
Journal Article
Peer reviewed
Open access
Although considerable effort has been devoted to investigating how birds migrate over large distances, surprisingly little is known about how they tackle so successfully the moment-to-moment ...challenges of rapid flight through cluttered environments 1. It has been suggested that birds detect and avoid obstacles 2 and control landing maneuvers 3–5 by using cues derived from the image motion that is generated in the eyes during flight. Here we investigate the ability of budgerigars to fly through narrow passages in a collision-free manner, by filming their trajectories during flight in a corridor where the walls are decorated with various visual patterns. The results demonstrate, unequivocally and for the first time, that birds negotiate narrow gaps safely by balancing the speeds of image motion that are experienced by the two eyes and that the speed of flight is regulated by monitoring the speed of image motion that is experienced by the two eyes. These findings have close parallels with those previously reported for flying insects 6–13, suggesting that some principles of visual guidance may be shared by all diurnal, flying animals.
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► Birds regulate flight speed by monitoring induced image motion (optic flow) ► Birds negotiate narrow passages safely by balancing lateral optic flow signals
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Birds flying through a cluttered environment require the ability to choose routes that will take them through the environment safely and quickly. We have investigated some of the strategies by which ...they achieve this. We trained budgerigars to fly through a tunnel in which they encountered a barrier that offered two passages, positioned side by side, at the halfway point. When one of the passages was substantially wider than the other, the birds tended to fly through the wider passage to continue their transit to the end of the tunnel, regardless of whether this passage was on the right or the left. Evidently, the birds were selecting the safest and quickest route. However, when the two passages were of equal or nearly equal width, some individuals consistently preferred the left-hand passage, while others consistently preferred the passage on the right. Thus, the birds displayed idiosyncratic biases when choosing between alternative routes. Surprisingly--and unlike most of the instances in which behavioral lateralization has previously been discovered--the bias was found to vary from individual to individual, in its direction as well as its magnitude. This is very different from handedness in humans, where the majority of humans are right-handed, giving rise to a so-called 'population' bias. Our experimental results and mathematical model of this behavior suggest that individually varying lateralization, working in concert with a tendency to choose the wider aperture, can expedite the passage of a flock of birds through a cluttered environment.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The extent to which brain structure is influenced by sensory input during development is a critical but controversial question. A paradigmatic system for studying this is the mammalian visual cortex. ...Maps of orientation preference (OP) and ocular dominance (OD) in the primary visual cortex of ferrets, cats and monkeys can be individually changed by altered visual input. However, the spatial relationship between OP and OD maps has appeared immutable. Using a computational model we predicted that biasing the visual input to orthogonal orientation in the two eyes should cause a shift of OP pinwheels towards the border of OD columns. We then confirmed this prediction by rearing cats wearing orthogonally oriented cylindrical lenses over each eye. Thus, the spatial relationship between OP and OD maps can be modified by visual experience, revealing a previously unknown degree of brain plasticity in response to sensory input.
There is scant published data about pulmonary hypertension (PH) from the developing countries. True prevalence of the disease, its biology, etiology and response to treatment are not well known, and ...they are likely to be somewhat different from that of the developed countries. In this review, we will discuss the main challenges for managing PH in developing countries and propose real-life recommendations to deal with such difficulties.
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Scedosporium prolificans are opportunistic moulds that can cause mycetoma following penetrating injuries. This fungus is more virulent than other species and treatment options are limited. Here we ...describe the first known case in the UK of S. prolificans osteomyelitis, in a 4 year old following penetrating injury. Successful outcome with limb salvage and foot function is achieved after repeated surgical debridement, and combination chemotherapy with voriconazole/terbinafine.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
INTRODUCTION: 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. RESULTS: 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. CONCLUSION: 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.
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