Is There Visual Lateralisation of the Sun Compass in Homing Pigeons?

Abstract

Functional lateralisation in the avian visual system can be easily studied by testing monocularly occluded birds. The sun compass is a critical source of navigational information in birds, but studies of visual asymmetry have focussed on cues in a laboratory rather than a natural setting. We investigate functional lateralisation of sun compass use in the visual system of homing pigeons trained to locate food in an outdoor octagonal arena, with a coloured beacon in each sector and a view of the sun. The arena was rotated to introduce a cue conflict, and the experimental groups, a binocular treatment and two monocular treatments, were tested for their directional choice. We found no significant difference in test orientation between the treatments, with all groups showing evidence of both sun compass and beacon use, suggesting no complete functional lateralisation of sun compass use within the visual system. However, reduced directional consistency of binocular vs. monocular birds may reveal a conflict between the two hemispheres in a cue conflict condition. Birds using the right hemisphere were more likely to choose the intermediate sector between the training sector and the shifted training beacon, suggesting a possible asymmetry in favour of the left eye/right hemisphere (LE/RH) when integrating different cues.

Spatial cognition and the avian hippocampus: Research in domestic chicks

“…In summary, our study (Morandi-Raikova and Mayer, 2021), together with the previous one by Tommasi et al (2003), highlights the importance of the right hippocampus of domestic chicks in processing spatial information, which is in line with some mammalian literature (Maguire et al, 1998;Spiers et al, 2001;Iglói et al, 2010;for reviews, see Klur et al, 2009;Oleksiak et al, 2011). Without going so far as to speculate about the evolutionary ancestry of hippocampal lateralization in vertebrates, we would like to emphasize that a left hemispheric dominance has been repeatedly proposed for navigation in pigeons (Ulrich et al, 1999;Gagliardo et al, 2001Gagliardo et al, , 2005Prior et al, 2004;Nardi and Bingman, 2007;Kahn et al, 2008;Mehlhorn et al, 2010;Jonckers et al, 2015;Griffiths et al, 2020). However, in pigeons, like in chicks, only few studies directly investigated hippocampal lateralization (Gagliardo et al, 2001(Gagliardo et al, , 2002(Gagliardo et al, , 2005Nardi and Bingman, 2007;Kahn et al, 2008;Mehlhorn et al, 2010;Jonckers et al, 2015).…”

Use of the sun compass by monocularly occluded homing pigeons in a food localisation task in an outdoor arena

“…In this condition, pigeons could rely on both sun compass information and colour beacons to localise the rewarded sector in the arena. Consistently to what was previously observed (Griffiths et al 2020 ) monocularly occluded pigeons were able to learn the task as well as binocular pigeons. However, differently from what was previously reported (Griffiths et al 2020 ), a significant difference between the learning performances of the two monocular groups emerged.…”

“…The experimental apparatus was an octagonal outdoor arena (2.6 m diameter and 0.90 m high) used in previous experiments (Chappell and Guilford 1995 ; Gagliardo et al 1996 , 2005 ; Griffiths et al 2020 ). The walls of the arena were made of opaque panels, preventing the view of the surroundings, covered by a mesh net allowing the view of the sky.…”

“…Sun compass orientation can be also studied in birds in semi-naturalistic settings, an experimental setting in which the animals could see the sky and rely on the sun compass. Pigeons are known to rely on sun compass information to localise a food reward in an outdoor arena either in the absence or presence of distinctive colour beacons placed on each sector (Bingman and Jones 1994 ; Gagliardo et al 1996 , 2005 ; Budzynski et al 2002 ; Griffiths et al 2020 ). The reliance on sun compass information is so strong that pigeons were shown to downgrade their reliance on visual beacons if the two kinds of information were set in conflict (Chappell and Guilford 1995 ).…”

“…Recently, an experiment on monocularly occluded pigeons trained in an outdoor arena provided with visual beacons did not highlight differences in sun compass-mediated spatial learning. However, pigeons with the left eye/right hemisphere in use showed a greater reliance on visual beacons when tested after the rotation of the arena, in order to set in conflict the sun compass directional information and the position of the visual beacons (Griffiths et al 2020 ). Nevertheless, this experiment leaves open the question about whether and to what extent the left or the right visual system may display an advantage in sun compass-mediated spatial tasks because the birds were not tested either in an arena void of visual beacons or in clock-shifted conditions.…”