Sneak peek: Raptors search for prey using stochastic head turns

Ochs, Michael F.; Zamani, Marjon; Gomes, Gustavo da Silva; Neto, Raimundo Cardoso de Oliveira; Kane, Suzanne Amador

doi:10.1642/auk-15-230.1

Cited by 6 publications

(8 citation statements)

References 60 publications

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“…In other species, head movements can occur when looking for food (Ochs et al, 2016) or when scanning for predators (Butler et al, 2016). Intermittent blinking might thus be quite widespread in animals.…”

Section: Discussionmentioning

confidence: 99%

Half-Blind to the Risk of Predation

Beauchamp¹

2017

Front. Ecol. Evol.

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Blinking serves several functions in animals, but it comes at the cost of intermittent blindness. Blinking can occur spontaneously, but it is commonly associated with head movements. As feeding animals often need to move the head down repeatedly to gather resources, intermittent blindness might represent a hitherto unappreciated cost of feeding. In addition, this cost might also be more prevalent in larger groups as feeding effort typically increases with group size. In chickens (Gallus gallus domesticus), blinks associated with head movements occurred at a high frequently during feeding bouts. While blinks tended to be short, the amount of time spent blinking was close to 50% when feeding and increased with group size. By contrast, time spent blinking was much lower when birds simply monitored their surroundings between feeding bouts. Intermittent blinking at this scale when feeding is likely to decrease the ability to detect predation threats in a timely fashion and to monitor neighbors effectively.

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Section: Discussionmentioning

confidence: 99%

Half-Blind to the Risk of Predation

Beauchamp¹

2017

Front. Ecol. Evol.

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“…This strong support for the log-normal distribution indicates that for these two features of sentinel behaviour the various forces shaping look duration acted in a multiplicative rather than in an additive fashion, which explains the right skew in the two empirical distributions. The log-normal distribution also fitted the distribution of look duration when raptors used head turns to search for nearby prey [ 35 ]. Right skew suggests that multiplicative processes might be a factor shaping visual search whether for predators or intruders as in Florida scrub-jays or for prey as in raptors.…”

Section: Discussionmentioning

confidence: 99%

“…With a rate of interruption that increases with time, for instance, short looks as well as longer looks would become less frequent than expected under the negative exponential distribution, yielding a humped distribution with a right skew. The Weibull family of exponential distributions can be used to model this situation [ 35 ].…”

Section: Methodsmentioning

confidence: 99%

Visual Monitoring Strategies of Sentinels in a Cooperative Breeder

Beauchamp¹,

Bowman

2022

Biology

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Vigilance is important for early detection of threats. Previous studies have focused on the allocation of time to vigilance but neglected how animals monitor their surroundings during vigilance. Where animals look and how long each look lasts can affect the quality of visual monitoring and thus the ability to detect threats during vigilance. We examined visual monitoring strategies in the Florida scrub-jay (Aphelocoma coerulescens), a cooperative breeder with sentinel behaviour. Sentinels in this species make head turns from vantage points to detect the arrival of predators and intruding neighbours. We found that sentinels initiated head turns at regular intervals and also returned their gaze to areas previously monitored at regular intervals, which is predicted when predators and intruders rely on surprise rather than stealth to approach. Sentinels made head turns in several directions, but often more frequently on one side of the body than the other, which was not predicted for regular vigilance. Average look duration during sentinel bouts was shorter in smaller groups and in juveniles. We argue that shorter looks are beneficial to increase visual coverage in more threatening situations. Our study highlights how visual monitoring strategies during vigilance reflect the risk posed by predators and intruders.

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“…Some meropids also hunt near rivers but in general this group utilizes open environments prone to wind (Hoyo et al, 2001). Hunting from mobile surfaces requires adaptations that provide greater stability such as head stabilization, so that a successful trajectory to a prey item can be achieved (Wallman and Letelier, 1993;Katzir et al, 2001Katzir et al, , 2018Ochs et al, 2017). In the coraciiforms with the anisodactyl-syndactyl morphology, greater stability is achieved through the fusion of pedal digits, which allows for less pedal movement [also accompanied by a reduction in musculature for the outer digits (Backus et al, 2015)] and a laterally placed expanded plantar surface with which to grasp surfaces which produces a firmer grip on mobile, and occasionally thin, perches through increased surface friction (Bock and Miller, 1959;Höfling and Abourachid, 2020).…”

Section: Ylsnhm01001mentioning

confidence: 99%

Exploring the Ecomorphology of Two Cretaceous Enantiornithines With Unique Pedal Morphology

Clark

O’Connor

2021

Front. Ecol. Evol.

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Recently, ∼100 Ma amber from Myanmar has become an important source of information regarding the morphology of Late Cretaceous enantiornithines. Two specimens consisting of partial hindlimbs exhibit unusual morphologies when compared to both extant avian taxa and other Cretaceous enantiornithines. Pedal morphology is extremely ecologically informative in Aves as it represents the interface between body and substrate. These seemingly bizarre pedal morphologies represent adaptations that allowed these birds to utilize certain niches present in their paleoenvironment. Specific ecological niches apply the same general pressures to different species over time, and in doing so, through natural selection, produce morphologies that function much the same, although they may be anatomically dissimilar. As such, extant animals can provide useful information pertaining to the functional morphology of extinct animals, even in the absence of direct analogs, as in the case of these two Hukawng enantiornithines. Comparisons to extant taxa in the same predicted niches of these enantiornithines can be used to either support or contradict previous hypotheses regarding the in vivo function of these unique pedal morphologies. Elektorornis chenguangi exhibits a hypertrophied third pedal digit, originally interpreted as an appendage used for probing. We support this interpretation, which allows informed speculation as to the cranial anatomy of this taxon since extant animals that probe in woody substrates consistently pair elongate probing structures with a second robust structure that functions as a means to penetrate into this hard substrate. This suggests that the rostrum of Elektorornis would have been robust and most likely edentulous. The second specimen YLSNHM01001 exhibits an unusually mediolaterally robust fourth pedal digit, nearly double the width of digit II. Given that no such morphology is present in any other bird in the Mesozoic or Cenozoic we feel the unusual morphology justifies erection of a new taxon, Fortipesavis prehendens gen. et sp. nov. Although distinct, the morphology in F. prehendens resembles the syndactyl condition in some extant avian groups, and we hypothesize the robust digit similarly functioned to increase the surface area of the foot, facilitating grip on perches through increased friction. The necessity for increased grip and the lateral placement of this digit may suggest F. prehendens utilized mobile perches similar to extant kingfishers.

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Sneak peek: Raptors search for prey using stochastic head turns

Cited by 6 publications

References 60 publications

Half-Blind to the Risk of Predation

Half-Blind to the Risk of Predation

Visual Monitoring Strategies of Sentinels in a Cooperative Breeder

Exploring the Ecomorphology of Two Cretaceous Enantiornithines With Unique Pedal Morphology

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