“…The bird with the highest acuity could detect a target subtending 0.091 deg of the visual field (5.48 cycles deg −1 ), while the bird with the lowest acuity could detect a target subtending 0.124 deg (4.04 cycles deg −1 ). Just as for stationary targets, the detection threshold for single black targets was lower than expected on the basis of grating acuity (7.7 to 10 cycles deg −1 ; Chaib et al, 2019 ; Haller et al, 2014 ; Lind and Kelber, 2011 ). Fig.…”
Section: Resultsmentioning
confidence: 57%
“…Thus, target acuity is theoretically limed by contrast sensitivity, while grating acuity is limited by the resolving power of the retina ( O'Carroll and Wiederman, 2014 ). In a recent study, we showed that this was not the case for budgerigars ( Melopsittacus undulatus , Shaw 1805) that have similar acuity for single targets and gratings ( Chaib et al, 2019 ). Budgerigars can resolve gratings with 7.7 to 10 cycles deg −1 , in which one black or white stripe subtends 0.05 to 0.065 deg of their visual field ( Haller et al, 2014 ; Lind and Kelber, 2011 ; Lind et al, 2012 ), while they can just detect single targets of between 0.065 and 0.098 deg size, depending on the luminance profile of the target ( Chaib et al, 2019 ).…”
Section: Introductionmentioning
confidence: 91%
“…In a recent study, we showed that this was not the case for budgerigars ( Melopsittacus undulatus , Shaw 1805) that have similar acuity for single targets and gratings ( Chaib et al, 2019 ). Budgerigars can resolve gratings with 7.7 to 10 cycles deg −1 , in which one black or white stripe subtends 0.05 to 0.065 deg of their visual field ( Haller et al, 2014 ; Lind and Kelber, 2011 ; Lind et al, 2012 ), while they can just detect single targets of between 0.065 and 0.098 deg size, depending on the luminance profile of the target ( Chaib et al, 2019 ). The main reason for this difference between humans and birds is presumably the birds' lower sensitivity for achromatic contrast ( Ghim and Hodos, 2006 ; Haller et al, 2014 ; Harmening et al, 2009 ; Hirsch, 1982 ; Hodos et al, 2002 ; Lind et al, 2013 , 2012 ; Orlowski et al, 2012 ; Potier et al, 2018 ; Reymond and Wolfe, 1981 ).…”
Section: Introductionmentioning
confidence: 91%
“…However, gratings rarely exist in nature, and thus, to understand how spatial resolution influences visually guided behaviour in an ecological context, other measures may be more interesting. For example, when asking at what distance a passerine can detect a conspecific, or a raptor can spot its prey, target acuity – which we define as the detection threshold, or the minimal resolvable angle, for small or distant single objects, might give a more relevant answer ( Chaib et al, 2019 ). In order to compare grating and target resolution, we assume that the size of the target (in degrees [deg] of visual field) equals half a cycle (one black or one white stripe) of a square wave grating.…”
Section: Introductionmentioning
confidence: 99%
“…During our previous experiment ( Chaib et al, 2019 ) it was surprisingly difficult to train budgerigars to the task of detecting stationary single targets. If the unexpectedly low visual acuity for stationary targets was influenced by the lack of motivation from the birds, this could potentially be overcome by movement of the target ( Pratt et al, 2010 ; Richard and Shawn, 2003 ).…”
For a bird, it is often vital to visually detect food items, predators, or individuals from the same flock, i.e. moving stimuli of various shapes. Yet, behavioural tests of visual spatial acuity traditionally use stationary gratings as stimuli. We have behaviourally tested the ability of budgerigars (Melopsittacus undulatus) to detect a black circular target, moving semi-randomly at 1.69 degrees second−1 against a brighter background. We found a detection threshold of 0.107±0.007 degrees of the visual field for target size corresponding to a resolution of a grating with a spatial frequency of 4.68 cycles degree−1. This detection threshold is lower than the resolution limit for gratings but similar to the threshold for stationary single objects of the same shape. We conclude that the target acuity of budgerigars for moving single targets, just as for stationary single targets, is lower than their acuity for gratings.
“…The bird with the highest acuity could detect a target subtending 0.091 deg of the visual field (5.48 cycles deg −1 ), while the bird with the lowest acuity could detect a target subtending 0.124 deg (4.04 cycles deg −1 ). Just as for stationary targets, the detection threshold for single black targets was lower than expected on the basis of grating acuity (7.7 to 10 cycles deg −1 ; Chaib et al, 2019 ; Haller et al, 2014 ; Lind and Kelber, 2011 ). Fig.…”
Section: Resultsmentioning
confidence: 57%
“…Thus, target acuity is theoretically limed by contrast sensitivity, while grating acuity is limited by the resolving power of the retina ( O'Carroll and Wiederman, 2014 ). In a recent study, we showed that this was not the case for budgerigars ( Melopsittacus undulatus , Shaw 1805) that have similar acuity for single targets and gratings ( Chaib et al, 2019 ). Budgerigars can resolve gratings with 7.7 to 10 cycles deg −1 , in which one black or white stripe subtends 0.05 to 0.065 deg of their visual field ( Haller et al, 2014 ; Lind and Kelber, 2011 ; Lind et al, 2012 ), while they can just detect single targets of between 0.065 and 0.098 deg size, depending on the luminance profile of the target ( Chaib et al, 2019 ).…”
Section: Introductionmentioning
confidence: 91%
“…In a recent study, we showed that this was not the case for budgerigars ( Melopsittacus undulatus , Shaw 1805) that have similar acuity for single targets and gratings ( Chaib et al, 2019 ). Budgerigars can resolve gratings with 7.7 to 10 cycles deg −1 , in which one black or white stripe subtends 0.05 to 0.065 deg of their visual field ( Haller et al, 2014 ; Lind and Kelber, 2011 ; Lind et al, 2012 ), while they can just detect single targets of between 0.065 and 0.098 deg size, depending on the luminance profile of the target ( Chaib et al, 2019 ). The main reason for this difference between humans and birds is presumably the birds' lower sensitivity for achromatic contrast ( Ghim and Hodos, 2006 ; Haller et al, 2014 ; Harmening et al, 2009 ; Hirsch, 1982 ; Hodos et al, 2002 ; Lind et al, 2013 , 2012 ; Orlowski et al, 2012 ; Potier et al, 2018 ; Reymond and Wolfe, 1981 ).…”
Section: Introductionmentioning
confidence: 91%
“…However, gratings rarely exist in nature, and thus, to understand how spatial resolution influences visually guided behaviour in an ecological context, other measures may be more interesting. For example, when asking at what distance a passerine can detect a conspecific, or a raptor can spot its prey, target acuity – which we define as the detection threshold, or the minimal resolvable angle, for small or distant single objects, might give a more relevant answer ( Chaib et al, 2019 ). In order to compare grating and target resolution, we assume that the size of the target (in degrees [deg] of visual field) equals half a cycle (one black or one white stripe) of a square wave grating.…”
Section: Introductionmentioning
confidence: 99%
“…During our previous experiment ( Chaib et al, 2019 ) it was surprisingly difficult to train budgerigars to the task of detecting stationary single targets. If the unexpectedly low visual acuity for stationary targets was influenced by the lack of motivation from the birds, this could potentially be overcome by movement of the target ( Pratt et al, 2010 ; Richard and Shawn, 2003 ).…”
For a bird, it is often vital to visually detect food items, predators, or individuals from the same flock, i.e. moving stimuli of various shapes. Yet, behavioural tests of visual spatial acuity traditionally use stationary gratings as stimuli. We have behaviourally tested the ability of budgerigars (Melopsittacus undulatus) to detect a black circular target, moving semi-randomly at 1.69 degrees second−1 against a brighter background. We found a detection threshold of 0.107±0.007 degrees of the visual field for target size corresponding to a resolution of a grating with a spatial frequency of 4.68 cycles degree−1. This detection threshold is lower than the resolution limit for gratings but similar to the threshold for stationary single objects of the same shape. We conclude that the target acuity of budgerigars for moving single targets, just as for stationary single targets, is lower than their acuity for gratings.
Predation risk may affect the foraging behavior of birds. However, there has been little research on the ability of domestic birds to perceive predation risk and thus adjust their feeding behavior. In this study, we tested whether domestic budgerigars (Melopsittacus undulatus) perceived predation risk after the presentation of specimens and sounds of sparrowhawks (Accipiter nisus), domestic cats (Felis catus), and humans, and whether this in turn influenced their feeding behavior. When exposed to visual or acoustic stimuli, budgerigars showed significantly longer latency to feed under sparrowhawk, domestic cat, and human treatments than with controls. Budgerigars responded more strongly to acoustic stimuli than visual stimuli, and they showed the longest latency to feed and the least number of feeding times in response to sparrowhawk calls. Moreover, budgerigars showed shorter latency to feed and greater numbers of feeding times in response to human voices than to sparrowhawk or domestic cat calls. Our results suggest that domestic budgerigars may identify predation risk through visual or acoustic signals and adjust their feeding behavior accordingly.
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