Bird Song Learning is Mutually Beneficial for Tutee and Tutor

Song learning is generally assumed to be beneficial for a young songbird, but merely incidental, without costs or benefits, for the older song ‘tutors’. In the present study we contrast two mutually exclusive hypotheses about the tutor/tutee relationship: (1) that it is cooperative, or at least mutually tolerant, with tutor and tutee mutually benefiting from their relationship, vs. (2) that it is competitive, with tutor and tutee competing over territory, so that one or the other suffers negative fitness consequences of their relationship. In a field study of three consecutive cohorts of song sparrows (Melospiza melodia) we determined the older bird (primary tutor) from whom the young bird (tutee) learned most of his songs, and how long tutee and primary tutor survived subsequently. We found that the more songs a tutee learns from his primary tutor, the longer their mutual survival on their respective territories. This study provides the first evidence of a mutual benefit of bird song learning and teaching in nature.

Mycobacteriosis in peafowl: Analysis of four cases

Peafowl (Pavo cristatus), similarly to other Galliformes, are particularly susceptible to infection by Mycobacterium avium. Peafowl differ from other Galliformes in the clinical image of the infection, with dominating respiratory signs. Occurrence of severe and sustained dyspnoea in peafowl raises suspicion of mycobacteriosis, which, however, is not always easy to confirm. In the cases described here, mycobacteria were detected in direct swabs from the trachea of two individuals, and cultures were conducted on the Löwenstein- Jensen medium. In one individual, no mycobacteria were found in tracheal swabs stained by the Ziehl-Neelsen method, despite the presence of clear clinical signs. The fourth case was a young bird submitted for necropsy. The cause of death was a mechanical trauma, but scarce caseous nodules typical of mycobacteriosis were found in the liver, spleen and lungs. The Mycobacterium avium isolates obtained from those cases were compared using (CCG)4-based PCR. A high similarity of three isolates of Mycobacterium avium subsp. avium was observed, two of which were derived from peafowl originating from the same farm, while the isolate from the fourth bird differed significantly and was identified by sequencing as Mycobacterium avium subsp. paratuberculosis..

Birdsong learning in the laboratory, with especial reference to the song of the Zebra Finch (Taeniopygia guttata)

Vocal imitation in songbirds exhibits interesting parallels to infant speech development and is currently the model system of choice for exploring the behavioural, molecular and electrophysiological substrates of vocal learning. Among songbirds, the Zebra Finch (Taeniopygia guttata) is currently used as the ‘flying mouse’ of birdsong research. Only males sing and they develop their song primarily during a short sensitive period in early life. They learn their speciesspecific song patterns by memorizing and imitating the songs of conspecifics, mainly adults. Since Immelmann's pioneering work, thousands of zebra finches have been raised in strictly controlled auditory environments to examine how their experience affected their songs. In this article, I review the different experimental procedures that have been used in the laboratory to study the social influences on song learning in the Zebra Finch. Poor song learning was observed using passive playback of taped songs, whereas self-eliciting exposure using operant tutoring techniques induced significant learning, but with a high interindividual variability. The success of the training paradigm is often measured by the quality of imitation of the songs to which the young bird is exposed. Using empirical evidence from the field and the laboratory, I will also discuss this issue, by summarizing possible advantages and disadvantages of producing a perfect imitation. So far, the best method to get a close copy of a song model in the Zebra Finch is to place a single young bird with an adult male. This situation, which is rather unnatural, does not meet the criteria for precise control necessary in experimental conditions. Optimizing the methods used to train a zebra finch to learn a song, in order to be able to predict the imitation success, will improve our understanding of the dynamics of vocal production learning. It would also consolidate this species as a research model of relevance to human speech development and disorders. Keywords: Zebra Finch; birdsong; learning; development; memory; social influences

The Role of Aggression in Song Tutor Choice in the Zebra Finch: Cause or Effect?

Young male zebra finches (Taeniopygia guttata) normally copy their song from one tutor when given a choice of two. Interaction is known to be a key feature of the learning process and this study examines the way in which one particular type of social behaviour, aggression, may affect tutor choice. Female raised zebra finches were given a choice of two song tutors, which had been pre-selected for differing levels of aggression, during the sensitive phase for song learning. A young bird was significantly more likely to learn from the tutor that was more aggressive to him, as found earlier by Clayton (1987). In addition, behavioural observations suggest that aggression towards the young bird was the cause rather than an effect of tutor choice. There was no significant relationship between the relative level of tutor aggression and the amount of his song copied. Changes in the level of aggression over the tutoring period are also discussed.

Nonshivering thermogenesis and adaptation to fasting in king penguin chicks

The ability to develop nonshivering thermogenesis (NST) and the effect of fasting on thermogenic response to cold were studied in winter-acclimatized king penguin chicks. Metabolic rate (MR) and integrated electrical muscle activity were measured at different ambient temperatures. In cold-acclimatized (5 degrees C) fed chicks, shivering threshold temperature (STT) was 9.4 degrees C lower than lower critical temperature (LCT), indicating that NST (0.7 W/kg) occurs at moderate cold, whereas in control chicks fed and reared at 25 degrees C for 3 wk, LCT and STT were similar. Chicks reared in the cold and fasting for 3 wk or 4-5 mo (natural winter fast) developed an NST of 0.8 and 2.4 W/kg, respectively, despite the fast. In fasting chicks, the intercept of the metabolic curve with the abscissa at zero MR was far below body temperature, contrasting with the classic model for heat loss. Their low LCT indicates the capacity of a large reduction in convective conductance characteristic of diving animals and allows energy sparing in moderate cold. Below LCT, conductance reincreases progressively, leading to a steeper than expected slope of the metabolic curve and allowing preservation of a threshold temperature in the shell. These results show for the first time in a wild young bird the development of NST after cold acclimatization. Further, at the temperature of cold acclimatization, an energy-sparing mechanism is shown in response to long-term fast adaptation.