Phonological-dependent territorial responses in yellowhammers (Emberiza citrinella).

In songbirds, males sing to attract potential mate and to defend their territory. Information about the sender such as its sex, its motivational state, its strength or identity can be encoded through subtle modifications in songs. In this study, we investigated whether territorial responses of yellowhammer males may be affected by modifications of song syntax and phonology. Yellowhammer song is mainly composed of three elements among which the last one is a long and low frequency note that is supposed to be the main component used by males to assess their potential rival. We carried out field experiments and played back either fully natural songs or partly natural and partly artificial songs to test this hypothesis. We identified that phonology rather than syntax modifications altered territorial responses. Our results also suggest that the phonology of the first song element plays a critical role in driving territorial responses.

Closed-loop bird-computer interactions: a new method to study the role of bird calls.

In the field of songbird research, many studies have shown the role of male songs in territorial defense and courtship. Calling, another important acoustic communication signal, has received much less attention, however, because calls are assumed to contain less information about the emitter than songs do. Birdcall repertoire is diverse, and the role of calls has been found to be significant in the area of social interaction, for example, in pair, family, and group cohesion. However, standard methods for studying calls do not allow precise and systematic study of their role in communication. We propose herein a new method to study bird vocal interaction. A closed-loop computer system interacts with canaries, Serinus canaria, by (1) automatically classifying two basic types of canary vocalization, single versus repeated calls, as they are produced by the subject, and (2) responding with a preprogrammed call type recorded from another bird. This computerized animal-machine interaction requires no human interference. We show first that the birds do engage in sustained interactions with the system, by studying the rate of single and repeated calls for various programmed protocols. We then show that female canaries differentially use single and repeated calls. First, they produce significantly more single than repeated calls, and second, the rate of single calls is associated with the context in which they interact, whereas repeated calls are context independent. This experiment is the first illustration of how closed-loop bird-computer interaction can be used productively to study social relationships.

Referential learning of French and Czech labels in African grey parrots (Psittacus erithacus): different methods yield contrasting results.

Some African grey parrots (Psittacus erithacus), the most famous being Pepperberg's parrot Alex, are able to imitate human speech and produce labels referentially. In this study, the aim was to teach ten African grey parrots from two laboratories to label items. Training three parrots from the first laboratory for several months with the Model/Rival method, developed by Pepperberg, in which two humans interact in front of the subject to demonstrate the use of a label, led to disappointing results. Similarly, seven parrots from the second laboratory, having been trained with several variants of Model/Rival attained little success. After the informal observation of the efficiency of other methods (i.e. learning to imitate labels either spontaneously or with specific learning methods and use of these labels referentially), four different teaching methods were tested with two birds: the Model/Rival; Repetition/Association which consisted of repeating a label and presenting the item only when the parrot produced the label; Intuitive in which the experimenter handled an item and repeated its name in front of the subject; Diffusion in which labels with either variable or flat intonation were played back daily to parrots. One bird learned three labels, one of which was used referentially, with the Repetition/Association method. He learned one label non-referentially with the Model/Rival but no labels were acquired using the other methods. The second bird did not learn any labels. This study demonstrates that different methods can be efficient to teach labels referentially and it suggests that rearing conditions and interindividual variability are important features when assessing learning ability of African grey parrots.

Spontaneous categorization of vocal imitations in African grey parrots (Psittacus erithacus).

The ability to categorize elements of the environment is a fundamental aspect of information processing. Many experiments demonstrate the ability of birds and non-human primates to classify items according to their perceptual similarities. Few data are available regarding spontaneous classification of items according to a non-perceptual account in non-human animals. Here, we report unexpected results obtained with African grey parrots learning the referential use of French labels. Parrots did not learn the correct labels but they spontaneously produced more labels corresponding to food when a food item was presented to them and more labels corresponding to an object when shown an object item, although they were never rewarded for doing so. These results demonstrate a form of spontaneous categorization by using vocal imitation of the human language.

Directional female preference for an exaggerated male trait in canary (Serinus canaria) song.

Motor constraints on vocal production impose a trade-off between trill rate and frequency bandwidth within birdsong. We tested whether domesticated canary (Serinus canaria) females, reared either in acoustic isolation or in aviary conditions, had a preference for broad bandwidth songs with artificially increased syllable rates. The copulation solicitation display (CSD) was used as an index of female preference. As predicted, both naive and experienced females were especially responsive to syllables with a broad bandwidth emitted at an artificially increased rate. Female preference for supernormal stimuli provide support for the honest-signalling hypothesis and our results are consistent with recent findings indicating that production of song phrases maximizing both bandwidth and syllable rate may be a reliable indicator of male physical or behavioural qualities. We suggest that female preference for vocal emissions, which simultaneously maximize these two parameters, could be a widespread pattern within songbirds.