Orientation and lateralized cue use in pigeons

over long distances has been studied extensively. In a typical homing experiment, pigeons are brought from their loft to release sites ranging from a few to tens of kilometres away, and their homing performance is measured. Standard parameters measured include the direction taken by the birds at the release site, the time until they vanish from the release site, and the time they take to return to their loft. Pigeons successfully home from totally unfamiliar sites. It is assumed that they can sense the direction of the loft by using a navigational map and that they use mechanisms such as a sun compass to keep their course. It is, however, still debatable which cues are used with the navigational map, and to what extent, and how the pigeons use visual cues related to prominent landscape features when homing through familiar terrain. Several studies support the view that visual aspects of the landscape are used during homing. When pigeons have the opportunity to preview a familiar landscape before departing they home faster than birds without this visual information (Braithwaite and Guilford, 1991; Braithwaite and Newman, 1994; Burt et al., 1997). Pigeons, however, tend to deviate in a predictable manner from the correct direction at familiar release sites if their sun compass is altered by clock-shifting (cf. Füller et al., 1983; Wiltschko and Wiltschko, 1998). Whether such findings are inconsistent with the pigeons’ use of visual information depends on the way they process this information. If they were ‘piloting’ by heading towards prominent landmarks, they should not deviate after a clockshift. If, however, they were using visual information just to recognize the site, they should show a systematic deviation. For example, when clock-shifted, pigeons with lesions to the hippocampus and released at familiar sites (Gagliardo et al., 1999) deviated to the full extent predicted by the clock-shift, whereas control pigeons showed only a small deviation from the home direction. This suggests that intact control birds derived directional information directly from the landmarks, while birds with hippocampal lesions used the landmark 1795 The Journal of Experimental Biology 205, 1795–1805 (2002) Printed in Great Britain © The Company of Biologists Limited JEB4051