Vision during head bobbing: are pigeons capable of shape discrimination during the thrust phase?

Abstract

Many birds show a characteristic forward and backward head movement, while walking, running and sometimes during landing flight, called head bobbing. During the hold phase, the head of the bird remains stable in space, while during the thrust phase, the head is rapidly moved forward. Three main functions for head bobbing have been proposed: Head bobbing might have a biomechanical cause, it might serve depth perception via motion parallax, or it might be an optokinetic response that primarily serves image stabilization for improved vision during the hold phase. To investigate vision during the different phases and in particular to test for visual suppression during the saccadic thrust phase, we tested pigeons on a shape discrimination task, presenting the stimuli exclusively either in the hold phase, thrust phase or at random times. Results clearly demonstrate that shape discrimination is as good during the thrust phase as it is during the hold phase.

On vision in birds: coordination of head-bobbing and gait stabilises vertical head position in quail

“…Birds do not bob their heads when walking or running on a treadmill [3] or when blindfolded [1]. The importance of head-bobbing for dynamic stability during terrestrial locomotion therefore seems to be negligible [9]. …”

“…Jiménez Ortega and colleagues [9] demonstrated in pigeons that shape discrimination during the thrust phase is as good as during the hold phase and concluded that unlike previously supposed [8,37], vision is not suppressed during the thrust phase [9]. Optic flow is more pronounced in the lateral field of view than in the frontal field [9] and more prone to suffer from translational and rotational perturbations [12]. The vertical stabilisation of the eye documented here, which is effected by gait-specific head-trunk coordination during terrestrial locomotion, is therefore advantageous to vision.…”

“…It comprises a hold phase (head position is fixed relative to the environment while the body continues to move forward) and a thrust phase (the head is thrust forward relative to the body; Figure 1A). This rapid forward movement of the head is believed to permit depth perception via motion parallax in a visual field with limited overlap between the left and the right eye [3,8,9]. Because the magnitude of the effect of motion parallax depends on the extent of head movement [10,11], depth cues are maximized and the largest difference in the apparent position of an object perceived if the eyes are moved in the direction of movement parallel to the ground.…”

Taking an insect-inspired approach to bird navigation

“…6b ). Just as insects move their heads to stabilize their view of the surrounding or generate optic flow, these bobbing movements both stabilize the image on retina, during the hold phase, and may generate visual motion cues, such as motion parallax, during the thrust phase (Jiménez Ortega, Stoppa, Güntürkün, & Troje, 2009 ). Birds can also generate motion parallax by peering , a behavior in which birds move their head side-to-side while perching (Kral, 2003 , Fig.…”

World in Motion: Perception and Discrimination of Movement in Juvenile Grey Bamboo Sharks (Chiloscyllium griseum)

“…Besides humans, various non-human species including mammals (primates: Brown, Kaplan, Rogers, & Vallortigara, 2010;Parron, Deruelle, & Fagot, 2007;Siegel & Andersen, 1988;Tomonaga, 2001;Vangeneugden, Vancleef, Jaeggli, VanGool, & Vogels, 2010;rats: Foley et al, 2012;MacKinnon, Troje, & Dringenberg, 2010;cats: Blake, 1993;dolphins: Herman, Morrel-Samuels, & Pack, 1990) and birds (e.g., Dittrich & Lea, 1993;Dittrich, Lea, Barrett, & Gurr, 1998;Ortega, Stoppa, Güntürkün, & Troje, 2009;Regolin, Tommasi, & Vallortigara, 2000;Troje & Aust, 2013;Vallortigara, Regolin, & Marconato, 2005;Vallortigara & Regolin, 2006;Zylinski & Osorio, 2013) have also been tested for their ability to recognize and distinguish biological motion patterns. Most species distinguished successfully between simple and complex biological and non-biological motion patterns; however, few were able to transfer or generalize their previously gained knowledge (e.g., MacKinnon et al, 2010;Vangeneugden et al, 2010).…”