A weak individual signature might not allow chick call recognition by parent Stone Curlews Burhinus oedicnemus

Offspring recognition has been confirmed in many bird species, and vocal signatures appear to be its major component. Up to now most studies dealt with colonial species, but recent findings indicate that similar recognition is also present in non-colonial birds. By integrating spectrographic analysis and playback experiments, we investigated for the first time parent–offspring vocal recognition in the Stone Curlew (Burhinus oedicnemus), a highly vocal, crepuscular-nocturnal species that usually rears a maximum of two precocial and nidifugous chicks. Even though the species is usually non-colonial and non-cooperative, in Taro River Regional Park, Parma, Italy, breeding territories are densely packed with distances between simultaneously active nests as close as 40 m, which creates the possibility that chicks might be exchanged. Our analysis identified two main vocalizations in the chick call repertoire: (1) the S-call, a brief strangled soft sound often uttered when parents and chicks were at close quarters; and (2) the C-call, a chirping sound with a complex structure, which seems to be a long-distance contact vocalization. Our acoustic analysis showed that, even though the structure was remarkably different between chicks, C-calls were an unreliable individual signature given their high intra-individual variability. This was confirmed by playback experiments. Indeed, when presented with simulated C-calling chicks, adults approached both their own and foreign chicks with equal responses. These results suggest that parent Stone Curlews are unable to recognize their offspring by voice. Furthermore, experiments are needed to test whether the chicks are able to recognize their parents' voice and, more generally, to understand the details of parent–offspring communication in this species

Productivity changes in the Mediterranean Sea drive foraging movements of yelkouan shearwater Puffinus yelkouan from the core of its global breeding range

Pelagic seabirds are tied to their breeding colonies throughout their long-lasting breeding season, but at the same time, they have to feed in a highly dynamic marine environment where prey abundance and availability rapidly change across space and seasons. Here, we describe the foraging movements of yelkouan shearwater Puffinus yelkouan, a seabird endemic to the Mediterranean Sea that spends its entire life cycle within this enclosed basin and whose future conservation is intimately linked to human-driven and climatic changes affecting the sea. The aim was to understand the main factors underlying the choice of foraging locations during the reproductive phases. A total of 34 foraging trips were obtained from 21 breeding adults tagged and tracked on Tavolara Archipelago (N Sardinia, Italy). This is the largest and most important breeding area for the species, accounting for more than 50% of the world population. The relationships between foraging movements during two different breeding stages and the seasonal changes of primary productivity at sea were modeled. Movements appeared to be addressed toward inshore (<20 km), highly productive, and relatively shallow (<200 m) foraging areas, often in front of river mouths and at great distances from the colony. During incubation, the Bonifacio Strait and other coastal areas close to North and West Sardinia were the most preferred locations (up to 247 km from the colony). During the chick-rearing phase, some individuals reached areas placed at greater distances from the colony (up to 579 km), aiming at food-rich hotspots placed as far north as the Gulf of Lion (France). The need for such long distance and long-lasting foraging trips is hypothesized to be related to unfavorable conditions on the less productive (and already depleted) Sardinian waters

A first assessment of genetic variability in the Eurasian Stone-curlew Burhinus oedicnemus

The Eurasian Stone-curlew is a species of conservation concern in Europe. We investigate for the first time the extent of population structure among populations sampled from six geographical areas, representing four subspecies inhabiting the western part of the species’ distribution. Neither mitochondrial nor nuclear markers fully supported current subspecies boundaries. However, both markers support significant differentiation of the Canary Island populations from those sampled from the Mediterranean. Further work is needed to establish the taxonomic status of this potentially distinct Macaronesian taxon. More broadly, further genetic research is required to design and implement an effective conservation plan for this species

Pattern of wing moult and its relationship to breeding in the Eurasian Stone-curlew Burhinus oedicnemus

SUMMARY: The timing, duration and pattern of the poorly documented wing moultin the Eurasian Stone-curlew Burhinus oedicnemus were described and related to the breeding cycle. Between 1998 and 2007, 141 birds were trapped in the Taro River Regional Park (Parma, Italy) both while incubating and during the post-breeding season. The timing of primary moult was estimated according to the method of Underhill & Zucchini (1988) and Underhill et al. (1990). Primary moult was very slow and overlapped most of the breeding season, beginning in early May and ending in October. Secondary moult was much more irregular and was not completed within a single moult cycle. Innermost and outermost secondaries were more likely to be shed than those at the centre of this tract. Juvenile secondaries were not shed during the first winter. The study provides the first detailed analysis of wing moult in the Eurasian Stone-curlew and suggests some useful ageing criteria based on the pattern of secondary moult. The extensive overlap between breeding and moulting is relatively uncommon compared to other waders. This could be interpreted as a way to maximize breeding success through renesting potential (up to 4 attempts), i.e. by spreading the cost of moult over a prolonged time period. A between-species comparison using independent contrasts was consistent with this hypothesis: species with a prolonged breeding season also showed considerable overlap in the timing of primary moult and breeding activitie

Landmark-based navigation in birds: learning and using topographical cues

This projects aims at understanding the role of visual cues in birds’ navigation and the involvement of the two brain hemispheres in processing familiar topographical landmarks by using GPS technology. 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. The GPS technology allowing the reconstruction of birds’ flight paths across the landscape with remarkable precision has been enhanced the research on landmark-based navigation in the last decade. Although familiar landmark-based navigation has been extensively studied, the use of familiar topographical features in wild birds’ navigation is still poorly understood. A crucial role of olfaction in oceanic navigation has been recently indicated in Cory’s shearwaters (a pelagic seabird), but whether seabirds might navigate by relying on topographical cues is still an open question. In this project three investigations have been conducted: i) the role of the environmental stimuli on Mediterranean navigation of Scopoli's shearwaters; ii) functional asymmetries in the visual system of pigeons in landmark-based spatial learning during homing; iii) involvement of the hippocampal formation in processing and using landscape visual cues. As concerning seabirds navigation, 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. The 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. Several studies in laboratory settings showed hemispheric specializations in visual tasks in birds. However, functional brain asymmetries in spatial behaviours in natural settings are still poorly investigated. We trained homing pigeons with a monocular occlusion (LH and RH with left eye and the right eye occluded and therefore processing the visual stimuli with the left and the right hemisphere, respectively) and unmanipulated control birds from two release sites. The monocular pigeons showed diminished tendency to fly in group in comparison to the control birds. However, the RH showed a stronger tendency to fly alone compared to the LH pigeons. In addition the RH birds displayed a higher fidelity to their most efficient route and were more efficient in localising home in the last phase of the homing process. After a clock-shift treatment when released in binocular condition, the birds of the three groups displayed a similar pattern of deviation from the last training track. However the RH birds showed a higher fidelity to the corridor identified by the tracks recorded during the last single training release in un-shifted condition. By contrast, the LH birds before re-orienting tended to fly for longer distances outside the previously visited area, compared to the RH birds. Our data suggest that there might be an advantage of the right hemisphere in memorising and using topographical cues in a re-orientation task during homing after clock-shift. Research in homing pigeons showed that the hippocampal formation (HF) is involved in familiar landmark-based navigation, while it seemed to play no role in navigation over unfamiliar space. 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 post-lesion 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 pre-lesion. 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

Only natural local odours allow homeward orientation in homing pigeons released at unfamiliar sites

According to the olfactory navigation hypothesis, birds are able to exploit the spatial distribution of environmental odourants to determine the direction of displacement and navigate from non-familiar locations. The so-called "olfactory activation hypothesis" challenged the specific role of olfactory cues in navigation by suggesting that olfactory stimuli only activate a navigational system that is based on non-olfactory cues, predicting that even artificial odourants alone are sufficient to allow unimpaired navigation. In this experiment, we compared tracks of experimental birds exposed to different olfactory stimuli before being made anosmic at the release site prior to release. One group of pigeons was exposed to purified air enriched with artificial odourants, while a second group was exposed to environmental air. The birds stimulated with artificial nonsense odourants displayed several behavioural differences from both untreated controls and anosmic pigeons exposed to environmental air prior to release: nonsense odourants birds were unable to determine the home direction, they mostly flew within a space outside the homeward oriented quadrant, and they flew shorter distances on the day of release. Our data failed to support a mere activational role of olfactory stimuli in navigation, and are consistent with the olfactory navigation hypothesis.publishe

Pigeon navigation : exposure to environmental odours prior release is sufficient for homeward orientation, but not for homing

The role of environmental olfactory information in pigeon navigation has been extensively studied by analysing vanishing bearing distributions and homing performances of homing pigeons subjected to manipulation of their olfactory perception and/or of the olfactory information they were exposed to, during transportation and at the release site. However, their behaviour during the homing flight remains undocumented. In this experiment we report the analysis of tracks of birds made anosmic at the release site by zinc-sulphate washing of their olfactory mucosa. We thus can assess the role of local odours at the release site as well as the role of environmental odours perceived on the way, far from the release site. We observed that pigeons transported and kept at the release site in purified air and made anosmic at the release site were unable to orient towards home and were impaired at homing. By contrast, pigeons allowed to smell environmental odours during transportation and at the release site, although made anosmic prior to release, displayed unimpaired homeward orientation, but nevertheless showed impaired homing performance. These results are consistent with the view that local odour at the release site are critical for determining the direction of displacement (olfactory map) and suggest that pigeons consult the olfactory map also during their homing flight in order to be able to find their way home.publishe

Only natural local odours allow homeward orientation in homing pigeons released at unfamiliar sites.

According to the olfactory navigation hypothesis, birds are able to exploit the spatial distribution of environmental odourants to determine the direction of displacement and navigate from non-familiar locations. The so-called “olfactory activation hypothesis” challenged the specific role of olfactory cues in navigation by suggesting that olfactory stimuli only activate a navigational system that is based on non-olfactory cues, predicting that even artificial odourants alone are sufficient to allow unimpaired navigation. In this experiment, we compared tracks of experimental birds exposed to different olfactory stimuli before being made anosmic at the release site prior to release. One group of pigeons was exposed to purified air enriched with artificial odourants, while a second group was exposed to environmental air. The birds stimulated with artificial nonsense odourants displayed several behavioural differences from both untreated controls and anosmic pigeons exposed to environmental air prior to release: nonsense odourants birds were unable to determine the home direction, they mostly flew within a space outside the homeward oriented quadrant, and they flew shorter distances on the day of release. Our data failed to support a mere activational role of olfactory stimuli in navigation, and are consistent with the olfactory navigation hypothesis

Pigeons remember visual landmarks after one release and rely upon them more if they are anosmic

Anosmic 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