Visual fields, foraging and collision vulnerability in <i>Gyps</i> vultures

Martin, Graham R.; Portugal, Steven J.; Murn, Campbell

doi:10.1111/j.1474-919x.2012.01227.x

Cited by 86 publications

(67 citation statements)

References 22 publications

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Section: Discussionsupporting

confidence: 62%

“…By contrast, the falcons in our previous study (Kane and Zamani, 2014) flew through the unobstructed sky, so viewing the prey at a lateral angle was unproblematic. As both species frequently fixed prey at nonzero visual angles, this supports the hypothesis that these birds may collide with man-made objects because they often focus attention away from their forward direction (Lima et al, 2014;Martin et al, 2012).Other taxa have been found to use different pursuit-evasion strategies for different scenarios, including flies (Land, 1993), fiddler crabs (Land and Layne, 1995) and bats (Chiu et al, 2010; Ghose et al, 2006). Consequently, we caution that these findings for goshawks and falcons need not apply in every circumstance.…”

supporting

confidence: 53%

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When hawks attack: animal-borne video studies of goshawk pursuit and prey-evasion strategies

Kane

Fulton

Rosenthal

2015

Journal of Experimental Biology

114

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Video filmed by a camera mounted on the head of a Northern Goshawk (Accipiter gentilis) was used to study how the raptor used visual guidance to pursue prey and land on perches. A combination of novel image analysis methods and numerical simulations of mathematical pursuit models was used to determine the goshawk's pursuit strategy. The goshawk flew to intercept targets by fixing the prey at a constant visual angle, using classical pursuit for stationary prey, lures or perches, and usually using constant absolute target direction (CATD) for moving prey. Visual fixation was better maintained along the horizontal than vertical direction. In some cases, we observed oscillations in the visual fix on the prey, suggesting that the goshawk used finite-feedback steering. Video filmed from the ground gave similar results. In most cases, it showed goshawks intercepting prey using a trajectory consistent with CATD, then turning rapidly to attack by classical pursuit; in a few cases, it showed them using curving non-CATD trajectories. Analysis of the prey's evasive tactics indicated that only sharp sideways turns caused the goshawk to lose visual fixation on the prey, supporting a sensory basis for the surprising frequency and effectiveness of this tactic found by previous studies. The dynamics of the prey's looming image also suggested that the goshawk used a tau-based interception strategy. We interpret these results in the context of a concise review of pursuit-evasion in biology, and conjecture that some prey deimatic 'startle' displays may exploit tau-based interception.KEY WORDS: Pursuit-evasion, Predator-prey, Avian vision, Northern Goshawk, Visual guidance, Sensory ecology, Accipiter gentilis, Looming, Antipredator behavior, Startle effect INTRODUCTIONMany problems in the study of animal behavior require an integrated biomechanical and sensory ecology approach that considers the organism's locomotor and perceptual capabilities, its sensory cues and the dynamics of its behavioral responses (Fernández-Juricic, 2012;Martin, 2012). Animal-borne video methods (Rutz and Troscianko, 2013) now make it possible to measure the visual cues received by organisms in the field, revealing new information about, for example, how they move through their environment (BBC, 2009), interact with conspecifics (Takahashi et al., 2004) and use tools (Rutz et al., 2007). Recent studies have used the stable video recorded by cameras mounted on the heads of birds (headcams) to explore the visual strategies used by falcons chasing prey (Kane and Zamani, 2014) and peafowl detecting model predators (Yorzinski and Platt, 2014). Here, we report using headcam video to explore for the first time pursuit-evasion and landing behavior in the Northern Goshawk, Accipiter gentilis (Linnaeus 1758) (hereafter, goshawk), a large diurnal raptor (Fig. 1). Biologically derived models have inspired robotic algorithms for swarming, following and collision avoidance (Mischiati and Krishnaprasad, 2012;Srinivasan, 2011), and the goshawk is of special inte...

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Section: Discussionsupporting

confidence: 62%

supporting

confidence: 53%

When hawks attack: animal-borne video studies of goshawk pursuit and prey-evasion strategies

Kane

Fulton

Rosenthal

2015

Journal of Experimental Biology

114

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“…Improving our knowledge on visual traits in raptors will improve insight into the evolution of anti-predator tactics and will also increase the efficiency of conservation programmes for raptors through a better understanding of their collisions with human-made devices Martin et al, 2012;McIsaac, 2001).…”

Section: Discussionmentioning

confidence: 99%

“…The visual fields of diurnal raptors have received little attention (Martin and Katzir, 1999;Martin et al, 2012;O'Rourke et al, 2010a) and they can differ significantly between species (O'Rourke et al, 2010a). Binocularity, for instance, plays a key role in the foraging behaviour of raptors, especially in the control of bill position and/or the position of the feet at the moment of prey capture .…”

Section: Introductionmentioning

confidence: 99%

Visual abilities in two raptors with different ecology

Potier

Bonadonna

Kelber

et al. 2016

Journal of Experimental Biology

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Differences in visual capabilities are known to reflect differences in foraging behaviour even among closely related species. Among birds, the foraging of diurnal raptors is assumed to be guided mainly by vision but their foraging tactics include both scavenging upon immobile prey and the aerial pursuit of highly mobile prey. We studied how visual capabilities differ between two diurnal raptor species of similar size: Harris's hawks, Parabuteo unicinctus, which take mobile prey, and black kites, Milvus migrans, which are primarily carrion eaters. We measured visual acuity, foveal characteristics and visual fields in both species. Visual acuity was determined using a behavioural training technique; foveal characteristics were determined using ultra-high resolution spectraldomain optical coherence tomography (OCT); and visual field parameters were determined using an ophthalmoscopic reflex technique. We found that these two raptors differ in their visual capacities. Harris's hawks have a visual acuity slightly higher than that of black kites. Among the five Harris's hawks tested, individuals with higher estimated visual acuity made more horizontal head movements before making a decision. This may reflect an increase in the use of monocular vision. Harris's hawks have two foveas (one central and one temporal), while black kites have only one central fovea and a temporal area. Black kites have a wider visual field than Harris's hawks. This may facilitate the detection of conspecifics when they are scavenging. These differences in the visual capabilities of these two raptors may reflect differences in the perceptual demands of their foraging behaviours.

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“…To date, modelling of risk to eagles from turbines in this region has been based simply on flight altitude, where low-altitude flight is classified as risky flight [41]. Because bird behaviour is likely to be directly linked to risk [42,43], a next generation of models could use flight classification algorithms to refine prediction risk by linking risk to specific low-altitude flight behaviours (foraging, use of orographic updraft).…”

Section: Classes (G-t O -G O -T)mentioning

confidence: 99%

Use of multiple modes of flight subsidy by a soaring terrestrial bird, the golden eagleAquila chrysaetos, when on migration

Katzner

Turk

Duerr

et al. 2015

J. R. Soc. Interface.

103

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Large birds regularly use updrafts to subsidize flight. Although most research on soaring bird flight has focused on use of thermal updrafts, there is evidence suggesting that many species are likely to use multiple modes of subsidy. We tested the degree to which a large soaring species uses multiple modes of subsidy to provide insights into the decision-making that underlies flight behaviour. We statistically classified more than 22 000 global positioning satellite-global system for mobile communications telemetry points collected at 30-s intervals to identify the type of subsidized flight used by 32 migrating golden eagles during spring in eastern North America. Eagles used subsidized flight on 87% of their journey. They spent 41.9% + 1.5 ( x + s:e:m:, range: 18-56%) of their subsidized northbound migration using thermal soaring, 45.2% + 2.1 (12-65%) of time gliding between thermals, and 12.9% + 2.2 (1-55%) of time using orographic updrafts. Golden eagles responded to the variable local-scale meteorological events they encountered by switching flight behaviour to take advantage of multiple modes of subsidy. Orographic soaring occurred more frequently in morning and evening, earlier in the migration season, and when crosswinds and tail winds were greatest. Switching between flight modes allowed migration for relatively longer periods each day and frequent switching behaviour has implications for a better understanding of avian flight behaviour and of the evolution of use of subsidy in flight.

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Visual fields, foraging and collision vulnerability in Gyps vultures

Cited by 86 publications

References 22 publications

When hawks attack: animal-borne video studies of goshawk pursuit and prey-evasion strategies

When hawks attack: animal-borne video studies of goshawk pursuit and prey-evasion strategies

Visual abilities in two raptors with different ecology

Use of multiple modes of flight subsidy by a soaring terrestrial bird, the golden eagleAquila chrysaetos, when on migration

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