( d– f) FPE (mean±s.e.m.) as a function of release for group A, B and C. ( a– c) Training protocols for the three experimental groups: A, B and C. One bird of group A and three birds of group B did not return to the loft. Training (maximum two releases per day) was conducted on consecutive days, interrupted only by unsuitable weather. By the end of training, each bird had performed 18 homing flights (six per site). releases alternating across the three RSs in a semi-random order).
single releases cycling in a consistent order through R1, R2 and R3) or (C) ‘random-order’ training (i.e. completing training at one site before commencing training at the next), (B) ‘rotation’ training (i.e. Training consisted of either (A) ‘sequential-site’ training (i.e. Each group experienced a distinct training protocol, defined by the sequence of releases from the three RSs ( figure 1 a–c). We used three different experimental groups of pigeons (A-, B- and C-pigeons). We released pigeons from three different release sites (henceforth RSs electronic supplementary material, figure S1): Stonesfield (R1 distance and direction to home: 10.4 km, 144°), Weston-on-the-Green (R2 10.2 km, 212°) and Beckley (R3 10.2 km, 264°). For every flight, geographical longitude and latitude were logged by the devices at 1 Hz (i-gotU GT-120 Phototrackers, Mobile Action Technology, Inc., Taiwan approx. During releases, all subjects carried GPS logging devices attached to their back by a small Velcro strip glued to clipped feathers. All experimental birds were less than two years old and had not participated in any previous experiment. We used 30 adult homing pigeons bred at the Oxford University Field Station (51☄6′58.34″ N, 1☁9′02.40″ W).
To answer this question, we used GPS technology to track the homing flights of pigeons repeatedly released from different sites either sequentially, in rotation or randomly. Here, we asked how homing efficiency is being influenced by the number of homing routes to be learned in parallel. While simultaneous storage of multiple targets and associated routes is likely to be the norm for pigeons, we do not know the extent to which the amount of spatial information that has to be handled to home reliably from different sites compromises the efficiency with which such information can be gathered and subsequently applied during homing. Now, their skills at faithfully following routes open up new avenues to explore in-flight learning and memory phenomena. Owing to their extraordinary capacity for visual discrimination, pigeons have been used to study learning and memory in the laboratory. However, it is not yet clear how efficiently they cope with the task of learning multiple homing routes. Pigeons carry out daily foraging flights to locations several kilometres away from the colony. These routes can be well characterized by two related measures, homing efficiency and track variation. Thus, it has been shown that pigeons flying over familiar terrain come to rely on stereotypical routes when homing repeatedly from the same site. Homing abilities have been most extensively studied in the pigeon, Columba livia. Their ability to return home from different places is therefore of great adaptive significance. The lives of many birds centre on a focal point in the environment, the colony or roosting site. The results of our study broaden our understanding of avian route following and open new possibilities for studying learning and memory in free-flying animals. Our data also indicated that they coped with increasing RS uncertainty by adjusting both their initial behaviour upon release and subsequent homing efficiency. We observed that pigeons from all groups successfully developed and applied memories of the different release sites (RSs), irrespective of the training protocol, and that learning several routes in parallel did not impair their capacity to quickly improve their homing efficiency over multiple releases. We subjected groups of pigeons to different training protocols, defined by the sequence in which they were repeatedly released from three different sites, either sequentially, in rotation or randomly. Here, we examined how learning multiple routes influences homing in pigeons. But it remains unknown how they cope with the task of learning several routes in parallel. For example, we know that pigeons ( Columba livia), long-standing models for avian navigation, rely on individually distinct routes when homing from familiar sites. The aerial lifestyle of central-place foraging birds allows wide-ranging movements, raising fundamental questions about their remarkable navigation and memory systems.
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