Person: Gagliardo, Anna
Gagliardo, Anna
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Gagliardo
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Anna
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- Data packageData from: Pigeons remember visual landmarks after one release and rely upon them more if they are anosmic(2020-09-24) Gagliardo, Anna; Pollonara, Enrica; Wikelski, MartinAnosmic birds' homing ability is impaired when challenged to navigate over unfamiliar areas. Nevertheless, anosmic pigeons, Columba livia, show unimpaired navigation when released within a familiar area, suggesting that they may rely on familiar visual landmarks for navigation. However, direct evidence for the reliance on familiar visual landmarks during homing in anosmic birds has never been provided. In this study we tracked pigeons subjected singly to one training flight from each of three locations. Prior to their second release from each site, half of the birds were made anosmic while the others were not manipulated. The level of route fidelity was analysed separately for three phases of the homing process, in which familiar visual cues may have different relevance and may be used within different cognitive strategies: (1) ‘Initial decision making’; (2) ‘En route navigation’; (3) ‘Local navigation around home’. Compared to control birds, the anosmic birds flew significantly closer to previously overflown locations in the ‘En route navigation’ phase, while no difference in route fidelity emerged during phases (1) and (3). Our results showed that a single experience is sufficient for pigeons to learn release site features, and that familiar visual landmarks constitute a critical source of navigational information in olfactorily deprived birds during the homing process.
- Data packageData from: Olfaction and topography, but not magnetic cues, control navigation in a pelagic seabird: displacements with shearwaters in the Mediterranean Sea(2015-10-27) Pollonara, Enrica; Luschi, Paolo; Guilford, Tim; Wikelski, Martin; Bonadonna, Francesco; Gagliardo, AnnaPelagic seabirds wander the open oceans then return accurately to their habitual nest-sites. We investigated the effects of sensory manipulation on oceanic navigation in Scopoli’s shearwaters (Calonectris diomedea) breeding at Pianosa island (Italy), by displacing them 400 km from their colony and tracking them. A recent experiment on Atlantic shearwaters (Cory’s shearwater, Calonectris borealis) breeding in the Azores indicated a crucial role of olfaction over the open ocean, but left open the question of whether birds might navigate by topographical landmark cues when available. Our experiment was conducted in the Mediterranean sea, where the availability of topographical cues may provide an alternative navigational mechanism for homing. Magnetically disturbed shearwaters and control birds oriented homeward even when the coast was not visible and rapidly homed. Anosmic shearwaters oriented in a direction significantly different from the home direction when in open sea. After having approached a coastline their flight path changed from convoluted to homeward oriented, so that most of them eventually reached home. Beside confirming that magnetic cues appear unimportant for oceanic navigation by seabirds, our results support the crucial role of olfactory cues for birds’ navigation and reveal that anosmic shearwaters are able to home eventually by following coastal features.
- Data packageData from: Identifying volatile organic compounds used for olfactory navigation by homing pigeons(2020-10-12) Zannoni, Nora; Wikelski, Martin; Gagliardo, Anna; Raza, Atif; Kramer, Stefan; Seghetti, Chiara; Wang, Nijing; Edtbauer, Achim; Williams, JonathanMany bird species have the ability to navigate home after being brought to a remote, even unfamiliar location. Environmental odours have been demonstrated to be critical to homeward navigation in over 40 years of experiments, yet the chemical identity of the odours has remained unknown. In this study, we investigate potential chemical navigational cues by measuring volatile organic compounds (VOCs): at the birds’ home-loft; in selected regional forest environments; and from an aircraft at 180 m. The measurements showed clear regional, horizontal and vertical spatial gradients that can form the basis of an olfactory map for marine emissions (dimethyl sulphide, DMS), biogenic compounds (terpenoids) and anthropogenic mixed air (aromatic compounds), and temporal changes consistent with a sea-breeze system. Air masses trajectories are used to examine GPS tracks from released birds, suggesting that local DMS concentrations alter their flight directions in predictable ways. This dataset reveals multiple regional-scale real-world chemical gradients that can form the basis of an olfactory map suitable for homing pigeons.
- Data packageData from: The homing pigeons’ olfactory map is affected by geographical barriers(2021-01-19) Gagliardo, Anna; Pollonara, Enrica; Wikelski, MartinThe factors affecting the olfaction-based navigational performances of homing pigeons released at relatively long distance (beyond 100 km from home) has in the past been subject to several investigations both in Germany and Italy using observations of vanishing bearing distributions. These studies highlighted the complexity of long-distance navigation in homing pigeons, which remains a poorly investigated aspect. In this tracking study we report how the homing performances of pigeons housed in Amino (Pisa, Italy) were affected by the presence/absence of a mountain range (the Northern Apennines) interposed between the home and the release site area (release sites: Trans = mountain barrier, Cis = no mountain barrier). We displaced unmanipulated control pigeons, anosmic pigeon, and pigeons transported in purified air to release sites located at a distance ranging between 95 and 246 km from home. There, birds were released without further manipulation. The navigational performances of anosmic pigeons were impaired at both Cis and Trans sites compared to both smelling groups. Both unmanipulated control pigeons and pigeons transported in purified air but allowed to smell environmental air at both the release site and after release displayed unimpaired navigational abilities at the Cis site, but impaired homing success and impaired homeward orientation at the Trans sites. Nevertheless, their homeward component was significantly greater than that of the anosmic birds at both geographical areas. This suggests that the Northern Apennine acts as a geographical barrier affecting the olfactory map accuracy of Amino pigeons, rather than totally reducing its spatial extent.
- Data packageData from: Homing pigeons only navigate in air with intact environmental odours: a test of the olfactory activation hypothesis with GPS data loggers [full dataset](2012-04-01) Gagliardo, Anna; Ioalè, Paolo; Filannino, Caterina; Wikelski, MartinA large body of evidence has shown that anosmic pigeons are impaired in their navigation. However, the role of odours in navigation is still subject to debate. While according to the olfactory navigation hypothesis homing pigeons possess a navigational map based on the distribution of environmental odours, the olfactory activation hypothesis proposes that odour perception is only needed to activate a navigational mechanism based on cues of another nature. Here we tested experimentally whether the perception of artificial odours is sufficient to allow pigeons to navigate, as expected from the olfactory activation hypothesis. We transported three groups of pigeons in air-tight containers to release sites 53 and 61 km from home in three different olfactory conditions. The Control group received natural environmental air; both the Pure Air and the Artificial Odour groups received pure air filtered through an active charcoal filter. Only the Artificial Odour group received additional puffs of artificial odours until release. We then released pigeons while recording their tracks with 1 Hz GPS data loggers. We also followed non-homing pigeons using an aerial data readout to a Cessna plane, allowing, for the first time, the tracking of non-homing homing pigeons. Within the first hour after release, the pigeons in both the Artificial Odour and the Pure Air group (receiving no environmental odours) showed impaired navigational performances at each release site. Our data provide evidence against an activation role of odours in navigation, and document that pigeons only navigate well when they perceive environmental odours.
- Data packageData from: GPS-profiling of retrograde navigational impairments associated with hippocampal lesion in homing pigeons(2021-06-15) Gagliardo, Anna; Colombo, Silvia; Pollonara, Enrica; Casini, Giovanni; Rossino, Maria Grazia; Wikelski, Martin; Bingman, Verner P.The avian hippocampal formation (HF) is homologous to the mammalian hippocampus and plays a central role in the control of spatial cognition. In homing pigeons, HF supports navigation by familiar landmarks and landscape features. However, what has remained relatively unexplored is the importance of HF for the retention of previously acquired spatial information. For example, to date, no systematic GPS-tracking studies on the retention of HF-dependent navigational memory in homing pigeons have been performed. Therefore, the current study was designed to compare the pre- and post-surgical navigational performance of sham-lesioned control and HF-lesioned pigeons tracked from three different sites located in different directions with respect to home. The pre- and post-surgical comparison of the pigeons’ flight paths near the release sites and before reaching the area surrounding the home loft (4 km radius from the loft) revealed that the control and HF-lesioned pigeons displayed similarly successful retention. By contrast, the HF-lesioned pigeons displayed dramatically and consistently impaired retention in navigating to their home loft during the terminal phase of the homing flight near home, i.e., where navigation is supported by memory for landmark and landscape features. The data demonstrate that HF lesions lead to a dramatic loss of pre-surgically acquired landmark and landscape navigational information while sparing those mechanisms associated with navigation from locations distant from home.
- Data packageData from: Evidence for pre-mnemonic, perceptual neglect of environmental features in hippocampal lesioned pigeons during homing(2014-07-31) Gagliardo, Anna; Pollonara, Enrica; Coppola, Vincent J; Santos, Carlos David; Bingman, Verner P.The importance of the vertebrate hippocampus in spatial cognition is often related to its broad role in memory. However, in birds, the hippocampus appears to be more specifically involved in spatial processes. The maturing of GPS-tracking technology has enabled a revolution in navigation research, including the expanded possibility of studying brain mechanisms that guide navigation in the field. By GPS-tracking homing pigeons released from distant, unfamiliar sites prior to and after hippocampal lesion, we observed, as has been reported previously, impaired navigational performance postlesion over the familiar/memorized space near the home loft, where topographic features constitute an important source of navigational information. The GPS-tracking revealed that many of the lost pigeons, when lesioned, approached the home area, but nevertheless failed to locate their loft. Unexpectedly, when they were hippocampal-lesioned, the pigeons showed a notable change in their behaviour when navigating over the unfamiliar space distant from home; they actually flew straighter homeward-directed paths than they did prelesion. The data are consistent with the hypothesis that, following hippocampal lesion, homing pigeons respond less to unfamiliar visual, topographic features encountered during homing, and, as such, offer the first evidence for an unforeseen, perceptual neglect of environmental features following hippocampal damage.
- Data packageData from: Importance of the hippocampus for the learning of route fidelity in homing pigeons(2020-09-29) Wikelski, Martin; Gagliardo, Anna; Bingman, Verner P.The avian hippocampal formation (HF) is thought to regulate map-like memory representations of visual landmarks/landscape features and has more recently been suggested to be similarly important for the perceptual integration of landmarks/landscapes. Aspects of spatial memory and perception likely combine to support the now well-documented ability of homing pigeons to learn to retrace the same route when homing from familiar locations, leading to the prediction that damage to the HF would result in a diminished ability to repeatedly fly a similar route home. HF-lesioned homing pigeons were repeatedly released from three sites to assess the importance of the hippocampus as pigeons gradually learn a familiar route home guided by familiar landmark and landscape features. As expected, control pigeons displayed increasing fidelity to a familiar route home, and by inference, successful perceptual and memory processing of familiar landmarks/landscape features. By contrast, the impoverished route fidelity of the HF-lesioned pigeons indicated an impaired sensitivity to the same landmark/landscape features.
- Data packageData from: Oceanic navigation in Cory’s shearwaters—evidence for a crucial role of olfactory cues for homing after displacement(2013-07-16) Gagliardo, Anna; Bried, Joël; Lambardi, Paolo; Luschi, Paolo; Wikelski, Martin; Bonadonna, FrancescoPelagic birds, which wander in the open sea most of the year and often nest on small remote oceanic islands, are able to pinpoint their breeding colony even within an apparently featureless environment, such as the open ocean. The mechanisms underlying their surprising navigational performance are still unknown. In order to investigate the nature of the cues exploited for oceanic navigation, Cory's shearwaters, Calonectris borealis, nesting in the Azores were displaced and released in open ocean at about 800 km from their colony, after being subjected to sensory manipulation. While magnetically disturbed shearwaters showed unaltered navigational performance and behaved similarly to unmanipulated control birds, the shearwaters deprived of their sense of smell were dramatically impaired in orientation and homing. Our data show that seabirds use olfactory cues not only to find their food but also to navigate over vast distances in the ocean.
- Data packageData from: Unilateral hippocampal lesions and the navigational performance of homing pigeons as revealed by GPS-tracking(2022-12-13) Gagliardo, Anna; Pollonara, Enrica; Bingman, Verner P.; Casini, GiovanniThe left and right hippocampal formation (HF) of the avian brain have been reported to control some different aspects of homing in pigeons. In the current study, we employed GPS-tracking technology and unilateral HF lesions to further explore what if any aspects of a pigeon’s homing flight might be under dominant control by either the left or right HF. Pigeons were released from three locations prior to any experimental manipulation and released repeatedly from the same three sites as sham-lesioned control, right HF-lesioned and left HF-lesioned treatment groups. Analyses of homing performance and virtual vanishing bearings revealed no effect of either lesion treatment. A more in-depth analysis of path efficiency during the initial decision-making, en route and near home phases of a homing flight also revealed no effect of either lesion treatment. A last analysis on the learning and memory for positions along a previously flown route, a proxy for investigating the development of route fidelity, also revealed no effect of either unilateral lesion. However, independent of treatment group, some statistically significant effects were observed with respect to changes in performance across training and the different release sites. The current study revealed no detectable difference between the left and right HF-lesioned pigeons with respect to several navigational parameters of a homing flight. Although in need of supporting experimentation, the results are consistent with the hypothesis that both the left and right HF are similarly able to support several aspects of homing pigeon navigation.