Behavioural factors influencing orientation and navigation in homing pigeons (Columba livia)

Die Heimkehrfähigkeit von Brieftauben widerspiegelt echte Navigation: sie bestimmen ihre Position und berechnen die Flugrichtung zum Heimschlag. Darüber hinaus dürften aber auch Verhaltensfaktoren die Heimkehrleistung beeinflussen. Ziel der Arbeit war das Erfassen der Rolle von Sozialverhalten, Erfahrung und Motivation auf den Heimflug mittels GPS-Loggern die von den Tauben mitgetragen wurden. Zuerst verglichen wir die Leistung von Einzeltauben mit Derjenigen kleiner Gruppen: Diese flogen schneller und besser gerichtet nach Hause. Dazu folgten die Gruppen weniger deutlich Autobahnen, ein Zeichen dass Schwarmbildung das Gleichgewicht zwischen Landmarken- und Kompassnavigation beeinflusst. Die Rolle der Erfahrung zeigte sich, indem zwei Gruppen parallel zur Küste aber aus gegensätzlichen Richtungen wiederholt trainiert wurden. Liess man diese Tauben auf dem Meer von einem Boot auf, von dem sie auf dem kürzesten Weg zum Heimschlag hätten fliegen können, so zeigten sie bis zur Küste eine deutliche Abweichung von diesem Kurs. Diese widerspiegelte klar die vorangegangene Trainingsrichtung. Schliesslich prüften wir ob die Wartezeit bis zum Auflass die Heimkehrmotivation beeinflusst. Tauben die am längsten warten mussten flogen am schnellsten, aber die relative Gerichtetheit ihres Fluges war im Vergleich zu den Frühstartern unverändert. GPS-Logging erfasst daher auch Verhaltensfaktoren und eröffnet so neue Perspektiven zur Analyse des Heimkehr und Navigationsverhalten. The remarkable homing abilities of homing pigeons reflect true navigation: they determine their position and calculate the direction to their home loft. Still, behavioural factors could have an effect on homing performance and directedness of flights. This study aimed to assess the effects of sociality, experience and homing motivation by tracking path and speed with GPS loggers carried by the birds. First, we compared individual homers and small flocks: flocks flew indeed faster and with more efficient paths. Moreover, flock-flying pigeons showed less road- following, suggesting that flocking shifts the balance between landmark and compass navigation toward the latter. We then tested the influence of experience by training two groups of pigeons from opposite directions with respect to the loft, and releasing them afterwards from a site at sea from which they could have flown to the loft directly and perpendicular to the training direction. This revealed a strong effect of experience as all birds showed, over the sea, a flight direction biased by the direction of previous training. Finally, we tested the effect of waiting time prior to release on homing parameters. Pigeons that waited the longest had faster flights and homing times, but measures of path efficiency remained unchanged. In conclusion, the use of GPS loggers assessed the influence of behavioural factors on pigeon homing, opening new perspectives in the study of bird navigation

Mediterranean storm petrels rely on nest position for homing after migration: a test with artificial nestboxes

Petrels are highly philopatric and return from migratory journeys of thousands of kilometres to breed in the same burrow year after year. During the breeding season, some burrowing petrel species rely on their sense of smell to locate their nest at night, but the mechanisms involved in the homing behaviour after several months at sea are virtually unknown. To understand whether the sense of smell is involved in nest finding at the return from migration and to study the interplay with other positional cues, we explored the homing behaviour and nest choice by Mediterranean storm petrels, Hydrobates pelagicus melitensis. During two consecutive winters, we conducted our research in a colony with well-used artificial nestboxes that has been studied for the past two decades. We experimentally displaced previously occupied nestboxes in late winter and then checked for nest choice and occupancy by breeding individuals in the following breeding season. This experimental design allowed the manipulation of the location of the burrow, and the olfactory information contained within, without manipulating other positional cues. We observed that almost all individuals nested in the nestbox located at the same position as the year before, regardless of whether the nestbox was the one they had previously occupied or another one. During the breeding period, we also tested in a Y-maze the olfactory preference for the occupied nestbox with respect to another random one. Again, storm petrels did not show any olfactory preference for their nest. Our study implies that storm petrels breeding in a cave rely on other positional cues than olfactory ones to home and suggests a mechanism combining tactile and proprioceptive cues to find the nest in the dark. (C) 2015 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.Peer reviewe

Anosmia impairs homing orientation but not foraging behaviour in free-ranging shearwaters

Shearwaters deprived of their olfactory sense before being displaced to distant sites have impaired homing ability but it is unknown what the role of olfaction is when birds navigate freely without their sense of smell. Furthermore, treatments used to induce anosmia and to disrupt magneto-reception in displacement experiments might influence non-specific factors not directly related to navigation and, as a consequence, the results of displacement experiments can have multiple interpretations. To address this, we GPS-tracked the free-ranging foraging trips of incubating Scopoli's shearwaters within the Mediterranean Sea. As in previous experiments, shearwaters were either made anosmic with 4% zinc sulphate solution, magnetically impaired by attachment of a strong neodymium magnet or were controls. We found that birds from all three treatments embarked on foraging trips, had indistinguishable at-sea schedules of behaviour and returned to the colony having gained mass. However, we found that in the pelagic return stage of their foraging trips, anosmic birds were not oriented towards the colony though coastal navigation was unaffected. These results support the case for zinc sulphate having a specific effect on the navigational ability of shearwaters and thus the view that seabirds consult an olfactory map to guide them across seascapes

Chemical labels differ between two closely related shearwater taxa

Chemical signals may be the basis of interspecific recognition and speciation in many animals. To test whether a chemical label allowing recognition between closely related species exists in seabirds, we investigated two closely related taxa breeding sympatrically at some localities: Cory's and Scopoli's shearwaters. Procellariiform seabirds are ideal for this study because they have a well‐developed olfactory system and unequalled associated capabilities among birds. We analysed and compared the relative volatile compounds composition of the uropygial gland secretions of Cory's and Scopoli's shearwaters. As the volatile components from uropygial secretions might also provide some critical eco‐chemical information about population origin and sex, we also examined variations in the volatile compounds between populations and sexes in Cory's shearwater. The chemical data were obtained using gas chromatography–mass spectrometry techniques looking for the presence of these three particular labels: species, population and gender. We found diagnostic differences in uropygial secretions between the two species of shearwaters and smaller but significant variation between populations of Cory's shearwater in the Atlantic. No significant differences were observed between males and females. Individuals might thus use the chemical variation between species to recognize and mate with conspecifics, especially at localities where both species breed sympatrically. Geographical variation in chemical composition of uropygial secretions suggests that selective forces might vary according to locality, and might represent a key in the species recognition. Further behavioural bioassays are needed to determine whether or not these species labels are signals allowing reproductive isolation between these two taxa. Finally, one of the aims of our study was to test easier methods than freezing for storing uropygial gland secretions in the field. We describe here a new possibility for the storage of uropygial secretion samples at ambient temperature in the field, providing an alternative, simple protocol for the sampling of avian chemosignals

Flock flying improves pigeons’ homing: GPS-track analysis of individual flyers versus small groups

The effects of aggregation in navigating animals have generated growing interest in field and theoretical studies. The few studies on the effects of group flying on the performance of homing pigeons (Columba livia) have led to controversial conclusions, chiefly because of the lack of appropriate technology to follow pigeons during their entire homeward flight. Therefore, we used GPS data-loggers in six highly pre-trained pigeons from a familiar release site first by releasing them six times individually, then six times as a group from the same site, and finally, again six times individually. Flight data showed that the homing performance of the birds flying as a flock was significantly better than that of the birds released individually. When flying in a flock, pigeons showed no resting episodes, shorter homing times, higher speed, and almost no circling around the start zone in comparison to individual flights. Moreover, flock-flying pigeons took a nearly direct, “beeline” route to the loft, whereas individually flying birds preferred to follow roads and other longitudinal landmarks leading towards the loft, even when it caused a detour. Our results show that group cohesion facilitates a shift towards more efficient homing strategies: individuals prefer navigating by familiar landmarks, while flocks show a compass orientation

EEG Responses to visual Landmarks in Flying Pigeons

BACKGROUND: GPS analysis of flight trajectories of pigeons can reveal that topographic features influence their flight paths. Recording electrical brain activity that reflects attentional processing could indicate objects of interest that do not cause changes in the flight path. Therefore, we investigated whether crossing particular visual landmarks when homing from a familiar release site is associated with changes in EEG. RESULTS: Birds carried both data-loggers for recording GPS position and EEG during flight. First, we classified characteristic EEG frequencies of caged birds and found five main bands: A: 0-3, B: 3-12, C: 12-60, D: 60-130, and E: 130-200 Hz. We analyzed changes in these activity bands when pigeons were released over sea (a featureless environment) and over land. Passing over the coastline and other prominent landmarks produced a pattern of EEG alterations consisting of two phases: activation of EEG in the high-frequency bands (D and/or E), followed by activation of C. Overlaying the EEG activity with GPS tracks allowed us to identify topographical features of interest for the pigeons that were not recognizable by distinct changes of their flight path. CONCLUSIONS: We provide evidence that EEG analysis can identify landmarks and objects of interest during homing. Middle-frequency activity (C) reflects visual perception of prominent landmarks, whereas activation of higher frequencies (D and E) is linked with information processing at a higher level. Activation of E bands is likely to reflect an initial process of orientation and is not necessarily linked with processing of visual information. Results Birds carried both data-loggers for recording GPS position and EEG during flight. First, we classified characteristic EEG frequencies of caged birds and found five main bands: A: 0–3, B: 3–12, C: 12–60, D: 60–130, and E: 130–200 Hz. We analyzed changes in these activity bands when pigeons were released over sea (a featureless environment) and over land. Passing over the coastline and other prominent landmarks produced a pattern of EEG alterations consisting of two phases: activation of EEG in the high-frequency bands (D and/or E), followed by activation of C. Overlaying the EEG activity with GPS tracks allowed us to identify topographical features of interest for the pigeons that were not recognizable by distinct changes of their flight path. Conclusions We provide evidence that EEG analysis can identify landmarks and objects of interest during homing. Middle-frequency activity (C) reflects visual perception of prominent landmarks, whereas activation of higher frequencies (D and E) is linked with information processing at a higher level. Activation of E bands is likely to reflect an initial process of orientation and is not necessarily linked with processing of visual information