Repeated training of homing pigeons reveals age dependent idiosyncrasy and visual landmark use.

Recent research into the navigational strategies of homing pigeons (Columba livia) inthe familiar area has highlighted the phenomenon of route fidelity – birds formingidiosyncratic flight paths to which they are loyal over multiple releases from the samesite, and even returning to this path when released from a near-by unfamiliar location.Such results highlight the potential importance of visual landmark cues in the homingprocess. However, not all birds have been shown to produce idiosyncratic routes orshow this route-joining behaviour. Here we use birds with and without flight experienceto study the formation of idiosyncratic routes when released repeatedly from a singlelocation, followed by two off-route releases with differing topography to see how flightexperience and local landmark features can influence navigational strategy in thefamiliar area. We found that, over the course of 20 sequential releases, birds withgreater flight experience tended to form idiosyncratic routes whereas less experiencedbirds did not show this tendency. When released from near-by sites (from which thebirds had not previously been released), a range of navigational strategies were seen,including flying parallel to the learned route (suggestive of a learned compassdirection), a direct flight path towards home (again indicative of compass use), re-joining the learned route, and following the coastline. These latter strategies aresuggestive of landmark usage. Analysis using time lag embedding was also used toassess the off-route releases, and the short-term correlation dimension valuesproduced (ranging from 1.5-2.5) were also indicative of strategies using one or twofactors (landmarks, compass, or a combination of these two). Individual birds oftenshowed different strategies at different sites, suggesting that the use of differentnavigational cues is highly flexible and situationally dependent