Apomorphine pecking in the pigeon.

Pecking activity elicited by apomorphine was studied quantitatively in intact and thalamic pigeons. While apomorphine pecking is easily observed in the intact pigeon, it is absent in the acute thalamic animal. I reappears, however, in the chronic preparation simultaneously with the recovery of spontaneous pecking. Apomorphine pecking is described by satiation and increased by fasting. Reticular stimulation produces reversible blockade of both apomorphine and spontaneous pecking with the same parameters, without increase in heart rate. Apomorphine pecking can be observed only in the presence of visual contrast, and is always aimed at the contrast points or edges. A decrease in contrast produces a decrease in the number of pecks delivered to the contrast points and an increase in those missing the target, while the total number of pecks delivered in a unit time is unaffected. A lowering of the background luminance is followed by a decrease in the total number of pecks, which is mostly due to a reduction of those aimed at the contrast points. All these findings are discussed and it is concluded that: i) apomorphine exerts an excitatory action (direct or indirect) on the hypothalamic feeding centers; hence apomorphine pecking can be considered as a pharmacologically motivated behavior; ii) visual contrast exerts a dual action on apomorphine pecking, namely it acts both as triggering stimulus and goal object; iii) the decrease in apomorphine pecking induced by lowering the ambient light intensity is probably due to a decrease in the level of the general arousal.     

The key mimetic features of hoverflies through avian eyes

Batesian mimicry occurs when a palatable species (the mimic) gains protection from predators by resembling an unpalatable or otherwise protected species (the model). While some mimetic species resemble their models closely, other species ('imperfect mimics') are thought to bear only a crude likeness. In an earlier study, pigeons (Columba livia) were trained to recognize wasp images in one experiment and non-mimetic (NM) fly images in another by rewarding the pigeons for pecking on the respective image types. These pigeons were subsequently presented with different images, including seemingly wasp-like hoverfly species, and the recorded peck rates on these images were used as a measure of the pigeons' perception of the hoverflies' mimetic similarity. To identify a candidate set of morphological features that the pigeons used when assessing this mimetic similarity, we first extracted a range of biometrical measurements from images originally presented to the pigeons. We then repeatedly optimized an empirical model in an attempt to match the recorded pigeon peck rates while using as few biometrical features as input as possible. Our models were able to fit the pigeon peck rates with considerable accuracy even while excluding many input features. Antennal length, a feature commonly used to discriminate between flies and wasps, was regularly retained as an input variable, but overall a different set of biometrical features was important for predicting the peck rates of pigeons rewarded for identifying wasps compared to those rewarded for identifying NM flies. In highlighting the importance of specific biometrical features in promoting mimicry and the irrelevance of others, our optimized models provide an explanation as to why certain species that appear to be poor mimics to humans are judged to be good mimics by birds.     

Spatial serial conditioning maintained with minimal temporal contingency

Two experiments used a spatial serial conditioning paradigm to assess the effectiveness of spatially informative conditioned stimuli in eliciting tracking behavior in pigeons. The experimental paradigm consisted of the simultaneous presentation of 2 key lights (CS2 and CTRL), followed by another key light (CS1), followed by food (the unconditioned stimulus or US). CS2 and CTRL were presented in 2 of 3 possible locations, randomly assigned; CS1 was always presented in the same location as CS2. CS2 was designed to signal the spatial, but not the temporal locus of CS1; CS1 signaled the temporal locus of the US. In experiment 1, differential pecking on CS2 was observed even when CS2 was present throughout the interval between consecutive presentations of CS1, but only in a minority of pigeons; prevalence of differential pecking was enhanced when CS2 duration was halved. A control condition verified that pecking on CS2 was not due to temporal proximity between CS2 and US. Experiment 2 demonstrated the reversibility of spatial conditioning between CS2 and CTRL. Asymptotic performance never involved tracking CTRL more than CS2 for any of 16 pigeons. It is inferred that pigeons learned the spatial association between CS2 and CS1, and that temporal contingency facilitated its expression as tracking behavior.     

Introductory remarks on this issue. On the role of the ampulla in disturbances of vestibular function.

The article reports on the use of pigeons as models in the study of vestibular dysfunction. In the experiment reported, the cupula was loosened by raising the endolymph pressure on one side of the ampulla. The pigeon eyes showed a nystagmus. One day later, the pigeons were able to stand upright, but with head tilted toward the side of operation. The pigeons were able to fly within 15 days. Vestibular defects added in some experimental birds resulted in an inability to regain flying capacity.     

Effects of methamphetamine on response rate: a microstructural analysis

Key pecking in pigeons was maintained under a multiple random-interval (RI) 1-min, RI 4-min schedule of food presentation. Several doses (0.3-5.6 mg/kg) of methamphetamine were administered, and effects on overall response rates and on the microstructure of responding were characterized. In three of the four pigeons, methamphetamine dose-dependently decreased overall response rate in both components; in the fourth pigeon, intermediate doses increased response rates. Log-survivor analyses did not produce the clear "broken-stick" pattern previously reported with rats [Shull, R.L., Gaynor, S.T., Grimes, J.A., 2001. Response rate viewed as engagement bouts: effects of relative reinforcement and schedule type. J. Exp. Anal. Behav. 75, 247-274]. A fine-grained analysis of inter-response times (IRTs) revealed clear bands of responding around certain IRT durations. Methamphetamine tended to decrease the frequency of IRTs in the shorter bands and increase the frequency of IRTs across all bins greater than 2s. These results suggest that (a) survivor analyses may not extend to pigeon key pecking, (b) microstructural analyses can reveal order not evident with overall response rate, and (c) a detailed analysis of responding might prove more useful than summary measures in characterizing drug effects on behavior.     

A direct effect of competition on food choice by pigeons

Previous research on food choice of pigeons foraging alone and in competition showed an indirect response to the competitor, mediated by the resource depletion associated with the competitor. This experiment showed, in addition, that pigeons can adjust their food choice in direct response to the competitor itself. Pigeons foraged for large, preferred grains of maize and smaller, unpreferred grains of wheat presented in bowls covered with sawdust. In a within-subject design, pigeons were tested alone or in competition with another pigeon. In competition, a higher choice proportion of the wheat grains was observed on the first two choices out of 48 items, and this effect increased with time in the experiment. This result underscores the role of learning in group foraging behaviour. It also suggests a possible ecological implication: that individuals that learn faster may enjoy a competitive advantage in terms of reduced delay in responding to the presence of a conspecific.     

Scrounger numbers and the inhibition of social learning in pigeons

Social foraging can inhibit the learning and performance of food-finding behaviours. Confusion, overshadowing and frequency-dependent payoffs may all contribute to the inhibition, but standard experimental procedures make the separation of these effects difficult. In this study, we combine characteristics of cage and aviary experiments and present either a single naive pigeon or groups of three naive pigeons with a pre-trained producer opening an apparatus in an aviary. All naive birds scrounged on the 3456 openings they witnessed. In a post-test given in the absence of other birds, all single scroungers opened the apparatus, but only one of the group-scrounging pigeons did. Scrounger numbers appear to play an important role in the inhibition of food-finding behaviour, suggesting that confusion is a major component of learning in a social context.     

Conditioning the pecking motions of pigeons

The spatio-temporal courses of head and neck motions of pigeons while pecking at small grains are described. Single and serial pecks are distinguished but the inter- and intraindividual variability of the peck kinetics is stressed. Pigeons were then trained with instrumental conditioning procedures to speed-up their pecking. A partial reinforcement schedule where pigeons had to peck repeatedly before receiving reward led to a mild shortening of inter-peck intervals at lower reinforcement rates but surprisingly, a lengthening at higher rates. A schedule where short inter-peck intervals were differentially rewarded yielded a pronounced abbreviation of the inter-peck intervals, but this was achieved by a reduction of the movement path rather than an increase in motion velocity. A schedule whereby increased approach velocities were differentially rewarded yielded marked movement accelerations. When pigeons were rewarded for diminished approach speeds they also showed significant movement decelerations. Finally, it is shown that pigeons could learn to reliably abort their peck approach movement when a visual stimulus signalling a penalty was occasionally presented during the approach movement. The proportion of successful peck interruptions decreased as these interruption signals occurred later during the approach phase. It is concluded that the pecking of pigeons is neither an innately fixed nor a visually ballistic movement. It is instead a multiply controlled and flexibly adaptable response pattern.     

Accurate route demonstration by experienced homing pigeons does not improve subsequent homing performance in naive conspecifics.

We describe an experiment that uses the grouping tendencies and navigational abilities of the homing pigeon (Columba livia) to investigate the possibility of socially mediated information transfer in a field setting. By varying the composition of paired-release types, we allowed some naive birds to receive an accurate demonstration of the home route whilst others were paired with similarly naive conspecifics. After this 'paired phase', we predicted that if any learning of spatial information occurred then naive members of the former pairs would outperform their untutored conspecifics when re-released individually during the subsequent 'single phase' of the experiment. This prediction was not confirmed. Neither homing speed nor initial orientation was superior in individually released tutored versus untutored birds, despite the fact that both performance measures were better in the earlier 'paired phase' with experienced demonstrators. Our results suggest that although naive homing pigeons clearly interact with their experienced partners, they are unable to transfer any individually useful spatial information to subsequent homing flights.     

Automatic imitation in budgerigars

A fully automated procedure, involving computer-controlled stimulus presentation and computer-recorded response measurement, was used for the first time to study imitation in non-human animals. After preliminary training to peck and step on a manipulandum, budgerigars were given a discrimination task in which they were rewarded with food for pecking during observation of pecking and for stepping during observation of stepping (Compatible group), or for pecking while observing stepping and for stepping while observing pecking (Incompatible group). The Incompatible group, which had to counter-imitate for food reward, showed weaker discrimination performance than the Compatible group. This suggests that, like humans, budgerigars are subject to 'automatic imitation'; they cannot inhibit online the tendency to imitate pecking and/or stepping, even when imitation of these behaviours interferes with the performance of an ongoing task. The difference between the two groups persisted over 10 test sessions, but the Incompatible group eventually acquired the discrimination, making more counter-imitative than imitative responses in the final sessions. These results are consistent with the associative sequence learning model, which suggests that, across species, the development of imitation and the mirror system depends on sensorimotor experience and phylogenetically ancient mechanisms of associative learning.     

Reaction to frustration in high and low feather pecking laying hens

Reaction to frustration of high (HFP) and low feather pecking (LFP) laying hens was investigated. From a HFP- and a LFP-line five birds with a HFP- and five birds with a LFP-phenotype were selected. Birds from the HFP-line were expected to show more key pecking and covered feeder pecking during frustration than birds from the LFP-line. When a bunch of feathers was presented, birds with a HFP-phenotype were expected to redirect their pecks at the bunch. Birds were trained to peck a key for a food reward in an automated Skinnerbox and subjected to two sessions: a control session, where food was available, and a frustration session, where the feeder was covered with Perspex. These two sessions were repeated in the presence of a bunch of feathers. Unexpectedly, birds from the LFP-line had a stronger reaction to frustration than birds from the HFP-line, expressed in pecking behaviour. When a bunch of feathers was offered, birds with a HFP-phenotype did not show more bunch pecking during frustration than birds with a LFP-phenotype.     

Extinction as discrimination: the molar view

The traditional molecular view of behavior explains extinction as the dissipation or inhibition of strength, formerly built up by contiguous reinforcement. In obstinate opposition to this explanation was the partial-reinforcement extinction effect: a partially reinforced response extinguishes more slowly than a continuously reinforced response. It suggests instead that extinction is discrimination. Four pigeons were exposed to daily sessions in which a variable period of food delivery, produced by pecking on a variable-interval schedule, was followed by extinction. The rate of food delivery was varied over a wide range across conditions. Varying the amount of food per delivery inversely with rate of delivery kept response rate from varying excessively. The results confirmed and extended the partial-reinforcement effect; persistence of pecking and time to extinction were inversely related to rate of obtaining food. The results support the molar view of extinction, not as loss of strength of a particular discrete response, but as a transition from one allocation of time among activities to another. Although molecular theories dismiss discrimination due to repeated training and extinction as an impurity or complication, repeated cycles of availability and privation are probably typical of the environment in which most vertebrate species evolved.     

Probability of Detecting Band-Tailed Pigeons During Call-Broadcast Versus Auditory Surveys

Abstract: Estimates of population trend for the interior subspecies of band-tailed pigeon (Patagioenas fasciata fasciata) are not available because no standardized survey method exists for monitoring the interior subspecies. We evaluated 2 potential band-tailed pigeon survey methods (auditory and call-broadcast surveys) from 2002 to 2004 in 5 mountain ranges in southern Arizona, USA, and in mixed-conifer forest throughout the state. Both auditory and call-broadcast surveys produced low numbers of cooing pigeons detected per survey route (x̄ ≤ 0.67) and had relatively high temporal variance in average number of cooing pigeons detected during replicate surveys (CV ≥ 161%). However, compared to auditory surveys, use of call-broadcast increased 1) the percentage of replicate surveys on which ≥1 cooing pigeon was detected by an average of 16%, and 2) the number of cooing pigeons detected per survey route by an average of 29%, with this difference being greatest during the first 45 minutes of the morning survey period. Moreover, probability of detecting a cooing pigeon was 27% greater during call-broadcast (0.80) versus auditory (0.63) surveys. We found that cooing pigeons were most common in mixed-conifer forest in southern Arizona and density of male pigeons in mixed-conifer forest throughout the state averaged 0.004 (SE = 0.001) pigeons/ha. Our results are the first to show that call-broadcast increases the probability of detecting band-tailed pigeons (or any species of Columbidae) during surveys. Call-broadcast surveys may provide a useful method for monitoring populations of the interior subspecies of band-tailed pigeon in areas where other survey methods are inappropriate.     

Transitions between cooperative and non-cooperative responding in the 'Pigeon's Dilemma'

Two pigeons played Iterated Prisoner's Dilemma (IPD) against a simulated opponent pre-programmed to play ‘Tit-For-Tat’ (TFT) and ‘Random’ (RND) strategies. Each pigeon received differential amounts of access to food following choices of either ‘cooperate’ or ‘defect’ on a trial. After 1000 trials against TFT and 500 trials against RND, results indicated that choice allocation was optimal when the birds played against RND but was sub-optimal when the birds played against TFT. In order to determine why the pigeons responded suboptimally against TFT, a trial-by-trial analysis of the data was conducted. The analysis revealed that once a pigeon had received the ‘Sucker's’ payoff (S), it was more likely to defect and receive the ‘Temptation’ payoff (T) than to cooperate and receive the ‘Reward’ (R) payoff. Local reinforcement contingencies appear to determine suboptimal responding against TFT in the iterated Pigeon's Dilemma.     

Identification and Molecular Analysis of Pathogenic Yeasts in Droppings of Domestic Pigeons in Beijing, China

Feral pigeons are known as reservoirs of pathogenic yeasts that cause opportunistic infections in human. In the outskirts of Beijing, China, pigeons are more frequently raised at homes than are encountered in public areas. Many studies have focused on the presence of pathogenic yeasts in the excreta (fresh or withered) of a variety kinds of birds, pigeon crop and cloacae. One hundred and forty-three samples of fresh droppings were collected from three suburban pigeon-raising homes in an area of northern Beijing, China. The internal transcribed sequences (ITS) of all strains (except for 8 strains of Rhodotorula sp. ) were sequenced and compared with those of the databases of the National Center for Biotechnology Information website ( http://www.ncbi.nlm.nih.gov ) using the Basic Local Alignment Search Tool (BLAST). Yeasts representing 8 genera, Cryptococcus, Filobasidium, Rhodotorula, Candida, Debaryomyces, Saccaromyces, Trichosporon and Sporidiobolus, were identified from 120 isolates. Cryptococcus was the most prolific genera represented by eight species. The populations of yeast species isolated from fresh pigeon droppings were different among homes. Although it is well established that Cryptococcus neoformans exists mainly in old pigeon guano, several C. neoformans strains were still isolated from fresh pigeon excreta, providing a clue that live cryptococcal cells could move through the gastrointestinal tract of the pigeons. Eight genera identified from fresh droppings of domestic pigeons further confirm that pigeons serve as reservoirs, carriers and even spreaders of Cryptococcus species and other medically significant yeasts. The proportion of pathogenic yeasts in all isolates is more than 90 %.     

Immunoelectrophoretic Analysis of Avian Ribonucleic Acid Tumor Virus Group-Specific Antigens

Tumors induced in pigeons by inoculation with the Schmidt-Ruppin strain of Rous sarcoma virus regressed after about 6 weeks. Sera from these pigeons, taken 8 weeks after inoculation, had complement-fixing group-specific antibody titers of 1:2 to 1:256. In immunoelectrophoresis with the pigeon serum, disrupted BAI strain A (myeloblastosis) avian tumor virus showed at least five precipitin arcs. The pattern of precipitin lines was dependent in part on the means used for virus disruption, and ethyl ether and nonionic detergents appeared to be both effective and relatively mild reagents. Immunoelectrophoretic comparison of pigeon serum with serum from a tumor-bearing hamster and that from virus-inoculated rabbits yielded similar, though not identical, results.     

Effects of 5-hydroxytryptophan on serotonin in nerve endings

—Preparations of synaptosomes (P₂) from the telencephalon and from the diencephalon plus optic lobes of the pigeon and from the telencephalon of the rat were used to study the effects of 5-hydroxytryptophan (5-HTP) on (a) the levels of serotonin (5-HT) in nerve endings and (b) the release of 5-HT from nerve endings. The levels of 5-HT were significantly higher (3.21 × 0.35 nmol/g original tissue weight) in the P₂ fraction isolated from the telencephalon of pigeons given intramuscular injections of 50mg/kg of d ,l -5-HTP in comparison to control values (1.42 ± 0.07). A similar twofold increase was observed with the P₂ fraction isolated from the diencephalon plus optic lobes. In addition, the levels of 5-HTP and 5-hydroxyindoleacetic acid also increased significantly in these P₂ fractions isolated from pigeons given d ,l -5-HTP injections in comparison to values obtained for pigeons given saline injections. In vitro studies using preparations of synaptosomes (from both pigeon and rat) labelled with [³H]5-HT indicated that 0.10 mil l -5-HTP increased the release of [³H]5-HT twofold over control values. A concentration as low as 0.001 mm l -5-HTP was tested on the P₂ fraction from the telencephalon of the pigeon and was found to significantly increase the release of [³H]5-HT over control values. This effect by l -5-HTP was blocked if a decarboxylase inhibitor was added to the medium. l -5-HTP at a concentration of 1.5 mm had no apparent effect on the release of [³H]norepinephrine or [³H]dopamine from synaptosomes prepared from the telencephalon of the rat or pigeon. The results are discussed in terms of the role of serotonin in producing certain types of behavioral depressions exhibited by pigeons and rats given injections of 5-HTP.