Altered Orientation and Flight Paths of Pigeons Reared on Gravity Anomalies: A GPS Tracking Study

The mechanisms of pigeon homing are still not understood, in particular how they determine their position at unfamiliar locations. The “gravity vector” theory holds that pigeons memorize the gravity vector at their home loft and deduct home direction and distance from the angular difference between memorized and actual gravity vector. However, the gravity vector is tilted by different densities in the earth crust leading to gravity anomalies. We predicted that pigeons reared on different gravity anomalies would show different initial orientation and also show changes in their flight path when crossing a gravity anomaly. We reared one group of pigeons in a strong gravity anomaly with a north-to-south gravity gradient, and the other group of pigeons in a normal area but on a spot with a strong local anomaly with a west-to-east gravity gradient. After training over shorter distances, pigeons were released from a gravitationally and geomagnetically normal site 50 km north in the same direction for both home lofts. As expected by the theory, the two groups of pigeons showed divergent initial orientation. In addition, some of the GPS-tracked pigeons also showed changes in their flight paths when crossing gravity anomalies. We conclude that even small local gravity anomalies at the birth place of pigeons may have the potential to bias the map sense of pigeons, while reactivity to gravity gradients during flight was variable and appeared to depend on individual navigational strategies and frequency of position updates.     

Do release-site biases reflect response to the Earth's magnetic field during position determination by homing pigeons?

How homing pigeons (Columba livia) return to their loft from distant, unfamiliar sites has long been a mystery. At many release sites, untreated birds consistently vanish from view in a direction different from the home direction, a phenomenon called the release-site bias. These deviations in flight direction have been implicated in the position determination (or map) step of navigation because they may reflect local distortions in information about location that the birds obtain from the geophysical environment at the release site. Here, we performed a post hoc analysis of the relationship between vanishing bearings and local variations in magnetic intensity using previously published datasets for pigeons homing to lofts in Germany. Vanishing bearings of both experienced and naïve birds were strongly associated with magnetic intensity variations at release sites, with 90 per cent of bearings lying within ±29° of the magnetic intensity slope or contour direction. Our results (i) demonstrate that pigeons respond in an orderly manner to the local structure of the magnetic field at release sites, (ii) provide a mechanism for the occurrence of release-site biases and (iii) suggest that pigeons may derive spatial information from the magnetic field at the release site that could be used to estimate their current position relative to their loft.     

Light-dependent information: influence of loft conditions on young pigeon’s navigational system

This study compares the initial orientation and homing performance of young inexperienced pigeons following their transportation to near and distant places in total darkness (treatment) and their subsequent release. The birds were housed in two lofts at the Lisbon Zoo. Each loft had its own specific features: the H-loft was exposed to prevailing winds and allowed an unhindered view of the surrounding landscape; the L-loft was protected from the wind and allowed only a partial view of the surroundings. Pigeons used in the release tests were between 6 and 7 weeks old. We found that, in general, the initial orientation of the pigeons was affected by the treatment: following release at near places, there was an increase in the scatter and a decrease the homeward component, suggesting that light-dependent information collected en route was used by young pigeons. The effect of the treatment was only temporary based on the observation that the homing performance was not affected. However, the distance of the release site strongly influenced the homing performances as pigeons appeared to be unable to home when released at locations distant from the loft. Based on the scatter or the homeward component, inter-loft differences were apparent with respect to different median vanishing intervals and the reactions of specific pigeons when subjected to the same treatment (transport in darkness) following release at near and distant places. These findings suggest that light-dependent information collected en route is a component of the young pigeon’s navigational system but that, at the young age of the birds tested here, it is preferentially used in familiar areas. In addition, the importance of the light-dependent information appears to depend upon prior experience obtained in the lofts.     

Pigeon Navigation: Different Routes Lead to Frankfurt

Background

Tracks of pigeons homing to the Frankfurt loft revealed an odd phenomenon: whereas birds returning from the North approach their loft more or less directly in a broad front, pigeons returning from the South choose, from 25 km from home onward, either of two corridors, a direct one and one with a considerable detour to the West. This implies differences in the navigational process.

Methodology/Principle Findings

Pigeons released at sites at the beginning of the westerly corridor and in this corridor behave just like pigeons returning from farther south, deviating to the west before turning towards their loft. Birds released at sites within the straight corridors, in contrast, take more or less straight routes. The analysis of the short-term correlation dimension, a quantity reflecting the complexity of the system and with it, the number of factors involved in the navigational process, reveals that it is significantly larger in pigeons choosing the westerly corridor than in the birds flying straight - 3.03 vs. 2.85. The difference is small, however, suggesting a different interpretation of the same factors, with some birds apparently preferring particular factors over others.

Conclusions

The specific regional distribution of the factors which pigeons use to determine their home course seems to provide ambiguous information in the area 25 km south of the loft, resulting in the two corridors. Pigeons appear to navigate by deriving their routes directly from the locally available navigational factors which they interpret in an individual way. The fractal nature of the correlation dimensions indicates that the navigation process of pigeons is chaotic-deterministic; published tracks of migratory birds suggest that this may apply to avian navigation in general.     

Magnetic position determination by homing pigeons?

How pigeons return home from unfamiliar release sites is a long-standing puzzle in animal behaviour. Walker (1998, 1999) has described a "vector summation model" which "identifies a novel coordinate that pigeons could use with magnetic total intensity to determine position". The model is not applicable in a magnetic field generated simply by a geocentric dipole, but requires a field perturbed by higher-order sources. Tests are devised to simulate the addition of both regional and local magnetic anomalies to a geocentric dipole field, and to calculate the directions of the home loft from a number of release sites. The results indicate that a pigeon would be unlikely to derive useful information from the model.     

Brieftauben

Homing pigeons Homing pigeons are well known for their excellent homing abilities which allow them to return to their lofts from unknown releasing sites more than hundreds of kilometres away. Several orientation mechanisms – sun compass, earth's magnetic field, olfactory cues, visual cues – are known to be involved in homing performance as well as parameters such as motivation and experience. New technology give an insight in their homing behaviour and track preferences and it is shown that homing pigeons physiology and neurobiology seem to be functionally adapted to homing. Pigeons races are still common and it is shown how the pigeon breeder tries to maximize the success of his pigeons.     

Anfangsorientierung und Heimkehrverhalten von Brieftauben unter dem Einflu? von Kurzwellen

Zusammenfassung Um den potentiellen Einfluß von Kurzwellen auf die Orientierung und das Heimkehrverhalten von Brieftauben zu testen, wurden zwei Schläge in der Nähe eines Kurzwellensenders eingerichtet, der eine der Strahlung voll ausgesetzt, der anderer in einem tagsüber nicht für Sendungen benutzten Sektor und zudem topographisch gegen den Sender geschützt. In beiden Schlägen wurden Jungtauben aufgezogen und im Alter von drei Monaten für Testflüge genutzt. Die mit bzw. ohne Kurzwellen am neuen Standort angewöhnten Alttauben sowie die mit bzw. ohne Kurzwellen an diesem Standort aufgewachsenen Jungtauben wurden von einem etwa 11 km entfernten Auflaßort für Heimflüge gegen den Sender mit und ohne Kurzwellen-Einfluß im relevanten Sektor eingesetzt.Es ergaben sich keine Unterschiede in der Anfangsorientierung zwischen den Versuchsgruppen. Dagegen flogen alle ohne Kurzwellen-Einfluß aufgewachsenen Gruppen tendenziell rascher heim, wenn kein aktueller Kurzwellen-Einfluß vorhanden war. Faßte man alle drei Gruppen zusammen, so wurde dieser Unterschied signifikant. Demgegenüber zeigten die beiden mit Strahlung aufgewachsenen Gruppen unter den beiden Strahlungsbedingungen keine unterschiedlichen Heimkehrgeschwindigkeiten. Die fünf Testgruppen zusammengefaßt zeigten geringere Flughöhen unter Kurzwellen-Einfluß. Diese Ergebnisse lassen darauf schließen, daß die Brieftauben die Kurzwellen fühlen können, daß aber ihre Anfangsorientierung dadurch nicht beeinträchtigt wird. Reduzierte Heimkehrgeschwindigkeiten und geringe Flughöhen unter Kurzwellen-Einfluß, deuten auf einen störenden Effekt der elektromagnetischen Felder hin. Das Verhalten der unter Kurzwellen aufgewachsenen juvenilen Gruppen erlaubt den Schluß, daß sich Tauben an gewisse Kurzwellenbedingungen gewöhnen können.

---

Initial orientation and homing behaviour of pigeons under the influence of short wave transmissions

Summary In order to test the potential influence of short wave radiation on the homing behaviour of pigeons we positioned two lofts with adult homing pigeons in the vicinity of a short wave transmitter. One loft was next to the transmitter and fully exposed to the radiation, the second protected against the radiation (a) by topographical features and (b) by its position in a sector that was not used for transmission during daytime. In both lofts young pigeons were raised and used for experimental flights at the age of three months. Adults accustomed to the new sites as well as young birds from the exposed and non-exposed lofts, respectively, were released some 11 km from the loft for homeward flights towards the transmitter, with and without transmission towards the relevant sector.Vanishing direction and vanishing time were not affected by the short wave radiation in any of the groups, thus corroborating earlier experiments with pigeons flying homewards from the transmitter towards distant lofts. However, all three groups raised in the absence of short wave radiation (A–, A+, J–) homed tendentially faster in situations where radiation was absent compared to situations with radiation. Pooled in one data set the three groups were significantly faster without radiation. On the other hand, the two juvenile groups raised under radiation (J1+ and J2+) homed at the same speed under both short wave situations. Furthermore, all five groups tended to choose lower flight altitudes when released under the influence of short wave radiation (significantly when groups were pooled). Besides the experiments, observations near the loft gave the impression that the pigeons kept in the exposed loft were reluctant to fly in the neighbourhood of the loft, particularly the adults.We conclude that short wave radiation can be felt by the pigeons, but does not interfere with their initial orientation. Reduced homing speeds of birds grown up without experiencing radiation, low flight levels in flights under radiation in all groups, and a general reluctance to fly of the pigeons next to the exposed loft, suggest that the radiation has an undefined negative effect on the birds. Unimpaired homing speeds in juveniles having grown up under varying field strengths suggest that homing pigeons can become accustomed to short wave radiation to a certain extent.

     

Pigeon homing along highways and exits

BACKGROUND: Anecdotal observations and early airplane and helicopter tracking studies suggest that pigeons sometimes follow large roads and use landmarks as turning points during their homeward journey. However, technical limitations in tracking pigeon routes have prevented proof. RESULTS: Here, we present experimental and statistical evidence for this strategy from the analysis of 216 GPS-recorded pigeon tracks over distances up to 50 km. Experienced pigeons released from familiar sites during 3 years around Rome, Italy, were significantly attracted to highways and a railway track running toward home, in many cases without anything forcing them to follow such guide-rails. Birds often broke off from the highways when these veered away from home, but many continued their flight along the highway until a major junction, even when the detour added substantially to their journey. The degree of road following increased with repeated releases but not flight length. Significant road following (in 40%-50% of the tracks) was mainly observed from release sites along northwest-southeast axis. CONCLUSIONS: Our data demonstrate the existence of a learned road-following homing strategy of pigeons and the use of particular topographical points for final navigation to the loft. Apparently, the better-directed early stages of the flight compensated the added final detour. During early and middle stages of the flight, following large and distinct roads is likely to reflect stabilization of a compass course rather than the presence of a mental roadmap. A cognitive (roadmap) component manifested by repeated crossing of preferred topographical points, including highway exits, is more likely when pigeons approach the loft area. However, it might only be expected in pigeons raised in an area characterized by navigationally relevant highway systems.     

Changes in the short-term deflector loft effect are linked to the sun compass of homing pigeons

Despite being the most studied of all avian orientation systems, important questions still remain about the sun compass of homing pigeons, Columba livia. White it is well-documented that the sun compass is usually learned by young pigeons during the first 10–12 weeks of life, the mechanism by which it is calibrated to adjust for seasonal changes in the sun's azimuth is not known with certainty. Previous experiments using short-term deflector loft pigeons indicated that the sun compass may be calibrated by referencing celestial polarization patterns. The present paper describes important measurable changes in the previously reported orientation behaviour of short-term deflector loft birds, and suggests a correlation between these changes and the presence of a massive upper-atmospheric dust cloud of volcanic origin which significantly altered natural skylight polarization patterns in 1982 and 1983. Moreover, it is shown that when the short-term effect was absent (at times when data from previous years suggested it should be present), the birds were also not using sun compass orientation, as demonstrated by their failure to show the standard ‘clockshift’ response to a 6-h fast shift of their internal clocks. These results support the hypothesis that reflected light cues, rather than odours, are the basis of the deflector loft effect in pigeon homing.     

Development of the navigational map in homing pigeons: effects of flight experience on orientation performance

Experiments have shown that pigeons, Columba livia, are able to develop navigational abilities even if reared and kept confined in an aviary, provided that they are exposed to the natural winds. In contrast, pigeons reared in a wind-screened aviary do not learn to navigate. Pigeons kept confined in a screened aviary when young do not learn to navigate even if, once they become adult, the screens are removed and the birds are exposed to natural winds for a period sufficiently long for map learning. In all of these experiments, pigeons were kept confined until the day of test release. In the present study we found that pigeons reared in a wind-screened aviary developed navigational abilities if, once adult, they were allowed to perform spontaneous flights around the loft. Nevertheless, their navigational performance never reached the level of controls.Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.      

Acetylcholine as sensory transmitter in crustacea

Summary In an attempt to learn more about the so-called map component in pigeon navigation, nine series of tests comprising 34 test releases were performed at a release site, 89 miles NNE of Ithaca, New York, where Cornell pigeons regularly depart nonrandomly but with a large clockwise deviation from the true home direction. The tests included releases of: (1) experienced pigeons new to the site, under sun; (2) pigeons with previous experience at the site, under sun; (3) experienced pigeons new to the site, under total overcast; (4) pigeons with previous experience at the site, under total overcast; (5) first-flight youngsters, under sun; (6) directionally trained pigeons; (7) pigeons from two other Ithaca-area lofts; (8) pigeons from two more distant lofts; (9) Bank Swallows from an Ithaca colony; (10) clock-shifted pigeons; (11) radio- and airplane-tracked pigeons.The results of these tests indicate that the directional bias of the Cornell pigeons is, in general, not dependent on weather conditions or on the previous experience of the birds. Moreover, a similar bias is shown by both pigeons from other Ithacaarea lofts and Bank Swallows from Ithaca. And a similar bias from their respective home directions is shown by birds from other areas. Clock-shifted pigeons departing more directly toward home have poorer homing success than controls. It is concluded that some environmental factor basic to the avian homing process is rotated clockwise at this release site, that biologically the birds are not making an error but are probably reading correctly a distorted map.I thank Irene Brown and Timothy Larkin for their aid in all phases of this project; Donald Windsor for help in two releases; Charles Walcott and Martin Michener for aid in airplane tracking; J. Downhower for collaboration in the radio tracking and swallow releases; Andre Gobert, Howard French, A. E. Newton, and Ludwig Karl for permitting me to use their pigeons, George Yerdon, Forest Ranger, and Andy Misura, District Ranger, New York State Department of Environmental Conservation, for their cooperation in making the facilities of the Castor Hill Fire Tower available to us; Monica Howland for preparing the drawings; and Bertha Blaker for typing. Research supported in part by NSF Grants GB-13046X and GB-35199X, and in part by Federal Hatch funds.     

Rats’ use of geometric, featural and orientation cues to locate a hidden goal

Over the past 20 years, a great deal of research has examined how different animals can use the geometric properties of the environment to determine their heading. Less well studied is how rats use the geometric properties of an environment to navigate, or determine the location, when it is not necessary to establish heading. Specifically, it is unclear to what extent rats still rely on geometric cues when they are not disoriented. In the current study, rats were trained to find food in one corner of a rectangular environment under either oriented or disoriented conditions. Probe tests placed geometric, featural and orientation cues in conflict. Results showed that featural cues exerted little control over the rats’ search preferences. All rats, whether trained while oriented or trained while disoriented, used geometric cues when these were the only cues available. Rats trained in the disoriented condition preferred geometric cues to orientation cues, whereas rats trained in the oriented condition showed more equal preference for orientation and geometric cues.     

Pigeon homing: The influence of topographical features in successive releases at the same site

A new device, the direction-recorder, offered the possibility to extend earlier studies of homing behaviour of pigeons when relevant topographical elements (mountains and large tracts of water) interpose between the release site and the home loft. Three series of experiments were carried out at three different sites to investigate intraindividual and interindividual variability in subsequent tosses from the same locality. Two release sites were chosen behind a mountain chain with respect to home; at the third site homeward directed route crosses the sea. From our results it turns out that homing pigeons may adopt different strategies. Moreover, a wide intraindividual variability was observed in repeated tosses at the same site; some pigeons remained faithful to the first route, whereas other birds tried successive new routes which, in most cases, were significantly shorter than previous ones. This result indicates that pigeons try, and are actually able, to improve their performance in subsequent releases from the same site.     

Homing pigeons subjected to section of the anterior commissure can build up two olfactory maps in the deflector lofts

Summary Pigeons kept in two cages with screens which deflect the wind clockwise (CW) or counterclockwise (CCW) show corresponding deflections in their initial orientation. In order to determine the nature of this phenomenon, experimental birds were treated as follows: 1. The anterior commissure of the forebrain (AC), which mediates the interhemispheric transfer of olfactory input was sectioned; 2. After surgery, each experimental bird was kept alternately in a CW cage with its right nostril plugged, and in a CCW cage with its left nostril plugged; the two treatments were alternated every 3 days for 69 days before test releases began. In 23 out of 28 cases the experimentals showed CW deflections when released with the right nostril plugged and CCW deflections when released with the left nostril plugged. The controls were intact, and their nostrils were free in each phase of the experiment. They were subdivided into two groups: one group was kept in the CW cage when the experimentals were in the same cage, the other group in the CCW cage when the experimentals stayed there. In the remaining time each group was kept in a fenced loft. The behaviour of controls demonstrated that the time the experimentals had spent in each kind of deflector cage had been long enough to produce the corresponding deflections in initial orientation. Control experiments were then performed on pigeons with the AC sectioned (2 series) and on intact birds (1 series), both maintained in lofts which did not deflect the wind, and released with one nostril plugged. They did not show deflections similar to those of the experimentals. The present results allow to conclude that the deflector loft effect is olfactory in nature, and that the AC sectioned pigeons, alternately subjected to different treatments in deflector cages are able to acquire two different odour maps for navigation.Abbreviations AC anterior commissure of the forebrain sectioned - CCW counterclockwise - CW clockwise     

Pigeon homing and magnetic fields: a response to Luschi et al. (1996)

This paper comments on an article ''Pigeon homing: evidence against reliance on magnetic information picked up en route at release sites'' by P. Luschi, C. del Seppia, E. Crosio and F. Papi, which appeared in this journal. It is pointed out that the particular effects which these authors show to be stress-induced artefacts are restricted to their specific strain of homing pigeons. The same effects could not be observed in pigeons from two other lofts: a difference in response that was shown to have a genetic base. In view of this, conclusions drawn from the results of Luschi et al. must be restricted to their own findings; they cannot be generalized to the other findings which indicate the use of magnetic outward journey information in young homing pigeons.     

Normal fluctuations in the earth's magnetic field influence pigeon orientation

Summary In an attempt to determine whether naturally occurring fluctuations in the earth's magnetic field influence homing pigeons' initial bearings, three series of test releases (1970, 1972, 1973) at a site 45.7 miles north of the loft were conducted under an experimental design that controlled for most extraneous variables. The mean bearings for each series showed a significant inverse correlation with the K index of magnetic activity, i.e. the bearings were more to the left when K was high. In a single series of releases at a site 43.6 miles west of the loft, the means again showed a significant inverse correlation with K. Since most of the magnetic fluctuations in all four series were less than 70 gamma, it is concluded that the sensitivity of pigeons to magnetic cues probably approaches that already demonstrated for honeybees. A brief discussion of Lamotte's (1974) paper concerning the effect of bar magnets on initial orientation is appended.     

Multivariate analysis of initial orientation in homing pigeons: Is there a “preferred compass direction”?

The mean vanishing direction of homing pigeons of a given release often deviates from the home direction considerably. Any kind of geographical systematic in these deviations might give us a hint on the distribution of the information involved in the homing process. Analysis of releases arranged symmetrically around the home loft with methods of circular statistics could not resolve the pending question of site-specificity vs. directional effects in the initial orientation of homing pigeons unambiguously. In part, this ambiguity comes about by the facts that

Pigeon Homing: The Orientation of Young Birds that had been Prevented from Seeing the Sun

To test whether the sun is an essential factor for the development of a functioning orientation system in birds, a group of young pigeons was raised as ‘No-Sun’-birds. They were not allowed to see the sun, and they were released to fly around their loft only under total overcast. The control group had an equal number of opportunities to fly under overcast plus additional flights under sun. When released as untrained birds under solid cloud cover, the ‘No-Sun’-birds were significantly oriented, whereas the controls were not. Small magnets glued between the wings (north toward the head) reversed the ‘No-Sun’-birds' orientation, indicating they used a magnetic compass. These findings show that the orientation system can develop without information from the sun. Differences in the orientation behavior of the ‘No-Sun’-birds and normally raised young pigeons are discussed.     

Pigeon homing: Further experiments on shielded lofts

• 1.1. Two series of experiments were performed by rearing homing pigeons in two corridor-lofts in each of which they could perceive winds from one direction only (340 and 160° in the first series, 250 and 70° in the second one).
• 2.2. In the first series the two groups of birds were differently, but not homeward, oriented.
• 3.3. In the second series the birds were homeward oriented only when released from sites lying along the directions from which they could sense wind at the home loft.

     

Pineal Body and Magnetic Sensitivity: Homing in Pinealectomized Pigeons under Overcast Skies

Since birds use the earth's magnetic field for compass orientation when astronomical cues are lacking and it has recently been suggested that the pineal body is part of their magnetic compass, test releases have been performed in overcast conditions with pigeons deprived of the pineal body. On the whole, both experimental and control birds were capable of homeward orientation, though the bearings of experimental were rather more scattered. No differences in homing speed or success were recorded. Thus, the pineal body does not appear to play an important role in the homing of pigeons.