Nigel I. Mann

Antiphonal four-part synchronized chorusing in a Neotropical wren

Plain-tailed wrens (Thryothorus euophrys) live in groups that sing synchronized choruses, the contributions of females and males alternating with each other in cycles, within which each sex sings two of the four parts, the whole achieving near perfect synchrony. As each bird has a repertoire of ca 20 phrases of each type, the synchrony also requires them to choose the same type at the same time as others of their sex. Songs can last up to 2 min, during which individuals join in and drop out. This must be one of the most complex singing performances yet described in a non-human animal.

Multiple functions to duet singing: hidden conflicts and apparent cooperation

Joint territory defence, mate guarding and pair bond formation are the three principal hypotheses put forward to explain the occurrence of duet singing in birds and primates. We tested predictions from all three hypotheses in a subspecies of the plain, or canebrake, wren, Thryothorus modestus zeledoni. This species performs one of the most complex antiphonal duet songs described, and we examined the function of these duets through a combination of observations and playback experiments. There has been little consensus on how to distinguish between the different hypotheses, and we combined experiments and observations to help to distinguish between the hypotheses in the field. Duets in this species appeared to function primarily in cooperative joint territory defence, but our results suggest that both males and females also used their contribution to the duet to mate-guard. We found evidence of learning duet performance after pair bond formation but, contrary to predictions, not in the temporal coordination of a pairs duets. Instead, more established pairs were more consistent in their duet repertoires than newly formed pairs, which combined their song types more randomly. We also found plasticity in the speed of duet performance, with pairs apparently adjusting the temporal pattern of their duet in response to different stimuli. We discuss the implications of these results for the use of duets in this species.

A comparative study of song form and duetting in neotropical Thryothorus wrens

The traditionally-defined wren genus Thryothorus is notable for its diversity of singing styles with some species producing highly coordinated duets or choruses in various formats while, at the other extreme, songs are performed almost exclusively by males. In this comparative study, we document the singing styles of almost all of the 27 or so species in this group, relating these to a molecular phylogeny in an effort to identify the conditions that have led to the evolution of duetting and chorus singing. In a previous study, we used molecular data to demonstrate that Thryothorus is actually paraphyletic, leading us to propose its splitting into three genera (one newly described) in addition to Thryothorus . Here we show that most species within each of these four genera usually sing with the same style, and that these styles tend to differ between the genera. We also show that a few species have songs that differ markedly from those most typical of their genus. We argue that these exceptional cases will provide important insights into the origins of duetting behavior, and tentatively suggest factors that may have played a role in determining the extent to which male and female birds combine their vocalizations together.

Social learning directs feeding preferences in the zebra finch, Taeniopygia guttata

Abstract We tested sexually mature zebra finches to see whether social learning influenced their feeding preferences, in particular whether they followed the preference of a male or a female demonstrator, of a red-ringed or a green-ringed male, and of a familiar or an unfamiliar male. Each observer was exposed to two demonstrators feeding at different-coloured hoppers, and then tested with a choice of hoppers to see which of the two colours they preferred. Males showed no preference between male and female demonstrators when choosing from which colour of food hopper to feed, but females preferred to feed from the hopper colour the male demonstrator had used. Both males and females exposed to male demonstrators wearing red or green leg rings fed preferentially from the same colour hopper as the red-ringed demonstrators had used. Finally, male birds exposed to familiar and unfamiliar demonstrators, preferred the food hopper from which the familiar demonstrator had fed. We interpret the results as indicating differences between the demonstrators in the amount of attention they attracted from observers. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.

THE COMPLEX SONG DUET OF THE PLAIN WREN

Abstract We studied the duet of the Caribbean-slope subspecies of the Plain Wren (Thryothorus modestus zeledoni) in Costa Rica. It is one of the most complex duets to have been described. The duet proper consists of rapid, highly coordinated alternation of “A-phrases” from the female and “B-phrases” from the male. While the female initiates this section with her A-phrase, this cyclical part of the duet is almost invariably preceded by an introductory “I-phrase” from the male, so that it is the male that initiates the performance. Each male has a repertoire of I- and B-phrases, and each female has a repertoire of A-phrases. These are specifically associated with each other to form a repertoire of duet types. We hypothesize that the pattern of song organization in this species facilitates more coordinated and precise duetting. The presence of the three components means that a full duet requires the cooperation of both members of the pair, strongly suggesting that it represents a mutually beneficial signal. El Canto en Dueto de Thryothorus modestus Resumen. En este trabajo estudiamos el canto en dueto de la subespecie caribeña Thryothorus modestus zeledoni en Costa Rica. El canto en dueto de esta especie es uno de los más complejos que se han descrito hasta la fecha. El dueto consiste en una serie de frases “A” por parte de la hembra y frases “B” por parte del macho alternadas de una manera altamente coordinada. A pesar de que la hembra inicia esta sesión de dueto con una frase “A”, esta parte del dueto es precedida invariablemente por una frase introductoria “I” del macho, de modo que el macho es el que inicia propiamente el canto. Cada macho tiene un repertorio de frases “I” y “B”, y cada hembra tiene un repertorio de frases “A.” Estas frases están estrechamente asociadas entre ellas para formar un repertorio de cantos en dueto. La hipótesis que proponemos es que el tipo de organización en el canto de esta especie facilita un canto en dueto más preciso y coordinado. La presencia de tres componentes hace que el canto en dueto requiera la cooperación absoluta de ambos miembros de la pareja. Esto sugiere que este tipo de señal beneficia a ambos sexos.

The influence of visual stimuli on song tutor choice in the zebra finch, Taeniopygia guttata

Abstract Young male zebra finches, given a choice of two song tutors belonging to different colour morphs during their sensitive phase for song learning, learned mainly from that belonging to the morph of the birds that reared them. When given only one song tutor, of a different morph from their parents, they were more likely to delay learning until after the normal sensitive phase or use elements in their song that were used by the father in his song. In mate choice tests, most young males preferred, a female of the same morph as that of the male from which they had learnt their song, but some did not do so, suggesting that song tutor choice and sexual imprinting are not manifestations of the same learning process.

Does leg-ring colour affect song tutor choice in zebra finches?

Young male zebra finches, Taeniopygia guttata, reared by their mothers alone showed no preference between males with red and with light-green colour rings in their choice of song tutor. Behavioural observations showed that the tutee associated more with the adult from which it was subsequently found to have learnt. In a second experiment, birds reared by both parents wearing either light-blue or light-green colour rings and then given a choice of tutors wearing these ring combinations also showed no preference between them. These young males did, however, more often approach the tutor ringed as their parents had been. This may explain why they did not show more interest in the tutor whose song they learnt. The majority of the tutors were used twice, with the ring colour swapped before they were used the second time. There was a strong tendency for the same male to be copied by the two young birds exposed to him. This could not be attributed to a difference in song rate between the two tutors. Further work will be required to discover the basis of that individuals greater attractiveness. Copyright 1999 The Association for the Study of Animal Behaviour.