Nocturnal homing in pigeons

• 1.1. A total of 541 pigeons from 3 populations was tested for the ability of nocturnal homing over increasing distances from 1 to 33 km.
• 2.2. Nocturnal homing over 20 km was an individual characteristic found only in a fraction of pigeons in a loft (30–35%). Its expression was not affected by variables influencing diurnal homing performance such as age, experience and breeding status.
• 3.3. This particular ability is likely to reflect superior navigational abilities related to non-visual orientation mechanisms.
• 4.4. The ability for nocturnal homing is probably genetically dependent: offspring from good nocturnal homers performed significantly better than offspring from poor homers.

     

Stable panoramic views facilitate snap-shot like memories for spatial reorientation in homing pigeons

Following spatial disorientation, animals can reorient themselves by relying on geometric cues (metric and sense) specified both by the macroscopic surface layout of an enclosed space and prominent visual landmarks in arrays. Whether spatial reorientation in arrays of landmarks is based on explicit representation of the geometric cues is a matter of debate. Here we trained homing pigeons (Columba livia) to locate a food-reward in a rectangular array of four identical or differently coloured pipes provided with four openings, only one of which allowed the birds to have access to the reward. Pigeons were trained either with a stable or a variable position of the opening on pipes, so that they could view the array either from the same or a variable perspective. Explicit mapping of configural geometry would predict successful reorientation irrespective of access condition. In contrast, we found that a stable view of the array facilitated spatial learning in homing pigeons, likely through the formation of snapshot-like memories.     

Learning multiple routes in homing pigeons

The aerial lifestyle of central-place foraging birds allows wide-ranging movements, raising fundamental questions about their remarkable navigation and memory systems. For example, we know that pigeons (Columba livia), long-standing models for avian navigation, rely on individually distinct routes when homing from familiar sites. But it remains unknown how they cope with the task of learning several routes in parallel. Here, we examined how learning multiple routes influences homing in pigeons. 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. 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. Our data also indicated that they coped with increasing RS uncertainty by adjusting both their initial behaviour upon release and subsequent homing efficiency. 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.     

The social transmission of a food-finding technique in pigeons: what is learned?

Experimentally-naive pigeons (Columba livia) were exposed to varying amounts of socially transmitted information needed for solving a food-finding problem. Observer pigeons that saw a trained bird (model) piercing the paper covering a food box and eating were able to solve the problem faster and more efficiently than pigeons that only saw the model eating but not piercing. This result held whether observer performance was simultaneous or deferred with respect to the model's demonstration. Pigeons that saw the model piercing but not eating showed almost no tendency to copy. These results suggest that copying was dependent upon observer recognition of the fact that the model was getting a food reward, and that pigeons were capable of learning aspects of the piercing technique by observation rather than by trial and error.     

The orientation of homing pigeons in relation to change in sun declination

Summary The sun navigation hypothesis ofMatthews is briefly reviewed with special reference to his sun occlusion experiment which supports this hypothesis. The results of a similar experiment are presented in which 13 young pigeons were kept from sight of the sun during a seven day period including the fall equinox while the sun height at noon decreased 3° 6.7. When the birds were released from a point 93 km. south of their loft they were exposed to a noon sun height equal to that of a point north of their home loft eight days earlier. Nevertheless they showed a northward orientation as did the 10 control birds with no difference in homing performance between the experimental and control groups. These results are not in agreement with those ofMatthews and do not support his sun navigation hypothesis.

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Zusammenfassung Die Sonnennavigations-Hypothese vonMatthews wird kurz besprochen, besonders im Hinblick auf den Warte-Versuch (Sun occlusion experiment), der unter anderem zur Prüfung der Hypothese angestellt wurde. Die Ergebnisse eines im Wilhelmshavener Gebiet angestellten Warteversuchs werden mitgeteilt: 13 Tauben wurden um die Herbst-Tagundnachtgleiche für 7 Tage ohne Sicht der Sonne gehalten, deren Mittagshöhe in dieser Zeit um 3° 6,7 abnahm. Als die Vögel 93 km südlich ihres Heimatorts aufgelassen wurden, befanden sie sich im Gebiet einer Mittags-Sonnenhöhe gleich der, welche vor der Warteperiode etwa 2° nördlich vom Heimatort herrschte. Trotzdem flogen sie gleich den Kontrollen nordwärts ab. Auch im Heimkehrerfolg bestand kein Unterschied zwischen Versuchs-und Kontrolltauben. Diese Ergebnisse stimmen mit den vonMatthews berichteten nicht überein und stützen seine Sonnen-Navigations-Hypothese nicht.

     

Insights from social transmission of information in rodents

Direct exposure to stimuli in their environment is not the only way that animals learn about important information. Individuals can infer fear from a social context through observation. Like humans, rats are very social animals, and may learn to infer information about their environment through their interactions with conspecifics. Here, we first review different models for social transmission of information in rodents. Second, we examine different modes of communication that are important to social learning. Then, we cover the different proximate factors that are thought to modulate the social transmission of information. Next, we identify social and environmental conditions that impact social learning, and finally, we conclude by revisiting social transmission through the lens of the Tinbergen framework.     

Effects of flight on blood parameters in homing pigeons

The influence of flight and flight duration on 13 blood parameters was studied in homing pigeons which returned after 2–22 h of flight from release sites 113–620 km away. The haematocrit value decreased from 54.4% in controls to 51.0% in the flown birds. A lowered haematocrit overproportionately improves blood flow. The plasma concentrations of glucose and l(+)-lactate did not differ between experimental and control birds. This is compatible with the idea that carbohydrates are utilized as fuel mainly in the initial phase of flight. Plasma free fatty acid levels were significantly increased during flight and triglyceride concentrations gradually decreased with progressive flight duration. These findings support the view that lipids are the main energy source during flight. Plasma uric acid concentrations were increased two- to fourfold in flown birds. Urea levels gradually rose with flight duration to 400% of controls. Plasma protein concentration was lowered in flown pigeons. These results hint to an increased protein degradation during flight. Na⁺, K⁺, Ca²⁺, and Mg²⁺ levels in the plasma of the flown pigeons were not significantly different from control values. This finding together with the urea/uric acid ratio indicates that no severe dehydration occurred in our pigeons during free-range flight.Abbreviations FA fatty acids - FFA free fatty acids     

The importance of environmental spatial heterogeneity and host social structure in disease transmission

[First paragraph]The spatial structure of a host population determines the spatial probability distribution of interaction between individuals, and therefore influences the spatio-temporal dynamics of disease transmission within the host population (Keeling, 1999; Gudelj and White, 2004). Nigel Barlow recognised this and included non-linear transmission in his later models (Barlow, 1991), simulating the result of spatial heterogeneity of risk in susceptible hosts. These models produced behaviour that could not be found in models with homogeneously mixed host populations: more rapid disease dynamics and a greater robustness of disease to control measures. However, in this model there was no causal mechanism driving the initial spatial heterogeneity of risk in host individuals. Environmental heterogeneity is likely to be a key factor in determining the spatial distribution of host individuals (Cronin and Reeve, 2005). We attempted to explore how environmental heterogeneity may affect disease dynamics via its influence on the spatial distribution of host individuals. We developed a spatially explicit stochastic model that incorporated spatially variable host density distributions, primarily driven by environmental heterogeneity.     

Small-scale spatial cognition in pigeons

Roberts and Van Veldhuizen's [Roberts, W.A., Van Veldhuizen, N., 1985. Spatial memory in pigeons on the radial maze. J. Exp. Psychol.: Anim. Behav. Proc. 11, 241-260] study on pigeons in the radial maze sparked research on landmark use by pigeons in lab-based tasks as well as variants of the radial-maze task. Pigeons perform well on open-field versions of the radial maze, with feeders scattered on the laboratory floor. Pigeons can also be trained to search precisely for buried food. The search can be based on multiple landmarks, but is sometimes controlled by just one or two landmarks, with the preferred landmarks varying across individuals. Findings are similar in landmark-based searching on a computer monitor and on a lab floor, despite many differences between the two kinds of tasks. A number of general learning principles are found in landmark-based searching, such as cue competition, generalization and peak shift, and selective attention. Pigeons also learn the geometry of the environment in which they are searching. Neurophysiological studies have implicated the hippocampal formation (HF) in avian spatial cognition, with the right hippocampus hypothesized to play a more important role in the spatial recognition of goal locations. Most recently, single-cell recording from the pigeon's hippocampal formation has revealed cells with different properties from the classic 'place' cells of rats, as well as differences in the two sides of the hippocampus.     

Interspecific social networks promote information transmission in wild songbirds

Understanding the functional links between social structure and population processes is a central aim of evolutionary ecology. Multiple types of interactions can be represented by networks drawn for the same population, such as kinship, dominance or affiliative networks, but the relative importance of alternative networks in modulating population processes may not be clear. We illustrate this problem, and a solution, by developing a framework for testing the importance of different types of association in facilitating the transmission of information. We apply this framework to experimental data from wild songbirds that form mixed-species flocks, recording the arrival (patch discovery) of individuals to novel foraging sites. We tested whether intraspecific and interspecific social networks predicted the spread of information about novel food sites, and found that both contributed to transmission. The likelihood of acquiring information per unit of connection to knowledgeable individuals increased 22-fold for conspecifics, and 12-fold for heterospecifics. We also found that species varied in how much information they produced, suggesting that some species play a keystone role in winter foraging flocks. More generally, these analyses demonstrate that this method provides a powerful approach, using social networks to quantify the relative transmission rates across different social relationships.     

The avian hippocampus, homing in pigeons and the memory representation of large-scale space

The extraordinary navigational ability of homing pigeons providesa unique spatial cognitive system to investigate how the brainis able to represent past experiences as memory. In this paper,we first summarize a large body of lesion data in an attemptto characterize the role of the avian hippocampal formation(HF) in homing. What emerges from this analysis is the criticalimportance of HF for the learning of map-like, spatial representationsof environmental stimuli used for navigation. We then exploresome interesting properties of the homing pigeon HF, using fordiscussion the notion that the homing pigeon HF likely displayssome anatomical or physiological specialization(s), comparedto the laboratory rat, that account for its participation inhoming and the representation of large-scale, environmentalspace. Discussed are the internal connectivity among HF subdivisions,the occurrence of neurogenesis, the presence of rhythmic thetaactivity and the electrophysiological profile of HF neurons.Comparing the characteristics of the homing pigeon HF with thehippocampus of the laboratory rat, two opposing perspectivescan be supported. On the one hand, one could emphasize the subtledifferences in the properties of the homing pigeon HF as possibledeparture points for exploring how the homing pigeon HF maybe adapted for homing and the representation of large-scalespace. Alternatively, one could emphasize the similarities withthe rat hippocampus and suggest that, if homing pigeons representspace in a way different from rats, then the neural specializationsthat would account for the difference must lie outside HF. Onlyfuture research will determine which of these two perspectivesoffers a better approximation of the truth.     

Polymorphism within theLDHA gene in the homing and non-homing pigeons

A total of 445 domestic pigeons were genotyped for the lactate dehydrogenase (LDHA) gene. Crude DNA was isolated from blood samples and feathers. Two polymorphic sites were identified in intron 6: one near the splice donor site GT is called site H and the other near the splice acceptor site is called site B. Interestingly, the nucleotide changes of both these sites associate perfectly with the A and B alleles of HaeIII polymorphism: the A allele with nucleotide A of site H and nucleotide T of site B; while the B allele with nucleotide G of site H and nucleotide G of site B. In this study, we have identified the molecular difference between alleles A and B of the pigeon LDHA gene. The difference at site H in intron 6 explains the HaeIII polymorphism. The frequencies of LDHAAB and LDHABB genotypes between the analysed groups differ significantly (P < 0.001); the LDHAA allele was more frequent in the groups of pigeons with elevated homing performance (P < 0.001). The functional difference may be due to the change at site B, the potential splice branch site. Since LDHA activity is associated with the homing ability, it is possible that during the process of selection for the homing ability, the LDHAA allele has been selected, and is more prevalent in the top-racing groups.     

The effects of hippocampal lesions in homing pigeons on a one-trial food association task

The role of the avian hippocampal formation in a one-trial food association task was investigated across various retention intervals. Control pigeons, lesioned controls, and pigeons with hippocampal formation lesions were allowed to find food hidden in one of four uniquely decorated bowls in a specific location in a room. After retention intervals of 10 min, 1 h, 7 h, and 24 h, pigeons were placed back in the room with the same bowl in the same location (unmanipulated trials) or with the previously rewarding bowl in a new location and a different bowl in the previously rewarding location (test trials). Although all groups chose the correct bowl during unmanipulated trials, hippocampal formation lesioned birds' choices to the bowl in the correct location decreased compared to the combined controls during the test trials. The results suggest that hippocampal formation lesions do not impair long-term memory of a goal after one experience but significantly decrease the use of spatial information to return to that goal. Accepted: 18 September 1999     

Hippocampal participation in the sun compass orientation of phase-shifted homing pigeons

The orientation of phase-shifted control and hippocampal lesioned homing pigeons with previous homing experience was examined to investigate the possible participation of the hippocampal formation in sun compass orientation. Hippocampal lesioned pigeons displayed appropriate shifts in orientation indicating that such birds possess a functional sun compass that is used for orientation. However, their shift in orientation was consistently larger than in control pigeons revealing a difference in orientation never observed in pigeons that have not undergone a phase shift. Although alternative interpretations exist, the data suggest the intriguing possibility that following a change in the light-dark cycle, the hippocampal formation participates in the re-entrainment of a circadian rhythm that regulates sun compass orientation.