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How Lovebirds Maneuver Rapidly Using Super-Fast Head Saccades and Image Feature Stabilization.

Kress D, van Bokhorst E, Lentink D - PLoS ONE (2015)

Bottom Line: High-speed flight recordings revealed that rapidly turning lovebirds perform a remarkable stereotypical gaze behavior with peak saccadic head turns up to 2700 degrees per second, as fast as insects, enabled by fast neck muscles.Similarly, before landing, the lovebirds stabilize the center of the perch in their visual midline.Similar gaze behaviors have been reported for visually navigating humans.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Stanford University, Stanford, California, United States of America.

ABSTRACT
Diurnal flying animals such as birds depend primarily on vision to coordinate their flight path during goal-directed flight tasks. To extract the spatial structure of the surrounding environment, birds are thought to use retinal image motion (optical flow) that is primarily induced by motion of their head. It is unclear what gaze behaviors birds perform to support visuomotor control during rapid maneuvering flight in which they continuously switch between flight modes. To analyze this, we measured the gaze behavior of rapidly turning lovebirds in a goal-directed task: take-off and fly away from a perch, turn on a dime, and fly back and land on the same perch. High-speed flight recordings revealed that rapidly turning lovebirds perform a remarkable stereotypical gaze behavior with peak saccadic head turns up to 2700 degrees per second, as fast as insects, enabled by fast neck muscles. In between saccades, gaze orientation is held constant. By comparing saccade and wingbeat phase, we find that these super-fast saccades are coordinated with the downstroke when the lateral visual field is occluded by the wings. Lovebirds thus maximize visual perception by overlying behaviors that impair vision, which helps coordinate maneuvers. Before the turn, lovebirds keep a high contrast edge in their visual midline. Similarly, before landing, the lovebirds stabilize the center of the perch in their visual midline. The perch on which the birds land swings, like a branch in the wind, and we find that retinal size of the perch is the most parsimonious visual cue to initiate landing. Our observations show that rapidly maneuvering birds use precisely timed stereotypic gaze behaviors consisting of rapid head turns and frontal feature stabilization, which facilitates optical flow based flight control. Similar gaze behaviors have been reported for visually navigating humans. This finding can inspire more effective vision-based autopilots for drones.

No MeSH data available.


Related in: MedlinePlus

Experimental apparatus and analysis techniques.(A) Box-shaped flight arena in which lovebirds performed a U-turn flight maneuver starting and ending at the perch. The maneuver was filmed in stereo with two high-speed cameras at 2000 fps. (B) Illustration of the four time points within a wing beat in which we assessed the head and body orientation in “low resolution” with respect to wing beat phase. Red dots depict marker points on the head used to obtain its position and yaw orientation. Blue dots depict tracked shoulder positions used to obtain the yaw orientation of the body. (C) Schematic camera view into the arena. Note that due to the indirect view via the mirror above the arena, camera images were mirrored around the horizontal axis. To avoid confusion, we will refer to the flight scene as seen from the camera perspective. Red and blue lines show how yaw orientations of the head and body were obtained relative to a horizontal line in the image.
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pone.0129287.g001: Experimental apparatus and analysis techniques.(A) Box-shaped flight arena in which lovebirds performed a U-turn flight maneuver starting and ending at the perch. The maneuver was filmed in stereo with two high-speed cameras at 2000 fps. (B) Illustration of the four time points within a wing beat in which we assessed the head and body orientation in “low resolution” with respect to wing beat phase. Red dots depict marker points on the head used to obtain its position and yaw orientation. Blue dots depict tracked shoulder positions used to obtain the yaw orientation of the body. (C) Schematic camera view into the arena. Note that due to the indirect view via the mirror above the arena, camera images were mirrored around the horizontal axis. To avoid confusion, we will refer to the flight scene as seen from the camera perspective. Red and blue lines show how yaw orientations of the head and body were obtained relative to a horizontal line in the image.

Mentions: For flight recordings, we trained five lovebirds (agapornis roseicollis) to turn on a dime in our custom-built flight arena (Fig 1A). The first step was to train the birds to fly between two perches. In the second step, one perch was removed and birds were trained to fly away, turn and return to the remaining perch. During the third step, the width of the perch was decreased to about 21 cm, after which the birds were ready for the experiment. The birds were 2 years old at the time of the experiments and their weights ranged between 47 g and 56 g (2LG, ♀, 54.8 g; 2DG, ♀, 53.8 g; 1Y, ♀, 47.1 g; 3Y, ♀, 55.6 g; 3G, ♂, 47.4 g). The air temperature during the experiments ranged between 20.8 and 21.6°C. The birds were housed in pairs in enriched cages in which they received food and water ad libitum. For kinematic high-speed tracking, we painted waterproof ink marker points (edding 750 paint marker, edding International GmbH, Ahrensburg, Germany) on specific parts of the bird’s head (Fig 1B). Depending on the bird’s plumage color, we chose either white or black paint to maximize the image contrast of the applied marker points.


How Lovebirds Maneuver Rapidly Using Super-Fast Head Saccades and Image Feature Stabilization.

Kress D, van Bokhorst E, Lentink D - PLoS ONE (2015)

Experimental apparatus and analysis techniques.(A) Box-shaped flight arena in which lovebirds performed a U-turn flight maneuver starting and ending at the perch. The maneuver was filmed in stereo with two high-speed cameras at 2000 fps. (B) Illustration of the four time points within a wing beat in which we assessed the head and body orientation in “low resolution” with respect to wing beat phase. Red dots depict marker points on the head used to obtain its position and yaw orientation. Blue dots depict tracked shoulder positions used to obtain the yaw orientation of the body. (C) Schematic camera view into the arena. Note that due to the indirect view via the mirror above the arena, camera images were mirrored around the horizontal axis. To avoid confusion, we will refer to the flight scene as seen from the camera perspective. Red and blue lines show how yaw orientations of the head and body were obtained relative to a horizontal line in the image.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4481315&req=5

pone.0129287.g001: Experimental apparatus and analysis techniques.(A) Box-shaped flight arena in which lovebirds performed a U-turn flight maneuver starting and ending at the perch. The maneuver was filmed in stereo with two high-speed cameras at 2000 fps. (B) Illustration of the four time points within a wing beat in which we assessed the head and body orientation in “low resolution” with respect to wing beat phase. Red dots depict marker points on the head used to obtain its position and yaw orientation. Blue dots depict tracked shoulder positions used to obtain the yaw orientation of the body. (C) Schematic camera view into the arena. Note that due to the indirect view via the mirror above the arena, camera images were mirrored around the horizontal axis. To avoid confusion, we will refer to the flight scene as seen from the camera perspective. Red and blue lines show how yaw orientations of the head and body were obtained relative to a horizontal line in the image.
Mentions: For flight recordings, we trained five lovebirds (agapornis roseicollis) to turn on a dime in our custom-built flight arena (Fig 1A). The first step was to train the birds to fly between two perches. In the second step, one perch was removed and birds were trained to fly away, turn and return to the remaining perch. During the third step, the width of the perch was decreased to about 21 cm, after which the birds were ready for the experiment. The birds were 2 years old at the time of the experiments and their weights ranged between 47 g and 56 g (2LG, ♀, 54.8 g; 2DG, ♀, 53.8 g; 1Y, ♀, 47.1 g; 3Y, ♀, 55.6 g; 3G, ♂, 47.4 g). The air temperature during the experiments ranged between 20.8 and 21.6°C. The birds were housed in pairs in enriched cages in which they received food and water ad libitum. For kinematic high-speed tracking, we painted waterproof ink marker points (edding 750 paint marker, edding International GmbH, Ahrensburg, Germany) on specific parts of the bird’s head (Fig 1B). Depending on the bird’s plumage color, we chose either white or black paint to maximize the image contrast of the applied marker points.

Bottom Line: High-speed flight recordings revealed that rapidly turning lovebirds perform a remarkable stereotypical gaze behavior with peak saccadic head turns up to 2700 degrees per second, as fast as insects, enabled by fast neck muscles.Similarly, before landing, the lovebirds stabilize the center of the perch in their visual midline.Similar gaze behaviors have been reported for visually navigating humans.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Stanford University, Stanford, California, United States of America.

ABSTRACT
Diurnal flying animals such as birds depend primarily on vision to coordinate their flight path during goal-directed flight tasks. To extract the spatial structure of the surrounding environment, birds are thought to use retinal image motion (optical flow) that is primarily induced by motion of their head. It is unclear what gaze behaviors birds perform to support visuomotor control during rapid maneuvering flight in which they continuously switch between flight modes. To analyze this, we measured the gaze behavior of rapidly turning lovebirds in a goal-directed task: take-off and fly away from a perch, turn on a dime, and fly back and land on the same perch. High-speed flight recordings revealed that rapidly turning lovebirds perform a remarkable stereotypical gaze behavior with peak saccadic head turns up to 2700 degrees per second, as fast as insects, enabled by fast neck muscles. In between saccades, gaze orientation is held constant. By comparing saccade and wingbeat phase, we find that these super-fast saccades are coordinated with the downstroke when the lateral visual field is occluded by the wings. Lovebirds thus maximize visual perception by overlying behaviors that impair vision, which helps coordinate maneuvers. Before the turn, lovebirds keep a high contrast edge in their visual midline. Similarly, before landing, the lovebirds stabilize the center of the perch in their visual midline. The perch on which the birds land swings, like a branch in the wind, and we find that retinal size of the perch is the most parsimonious visual cue to initiate landing. Our observations show that rapidly maneuvering birds use precisely timed stereotypic gaze behaviors consisting of rapid head turns and frontal feature stabilization, which facilitates optical flow based flight control. Similar gaze behaviors have been reported for visually navigating humans. This finding can inspire more effective vision-based autopilots for drones.

No MeSH data available.


Related in: MedlinePlus