Laurent Nagle

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.

In a songbird, the black redstart, parents use acoustic cues to discriminate between their different fledglings

Several studies on parental investment in territorial songbirds have reported the existence of brood division. This is a type of postfledging care in which each parent has long-term feeding preferences for different young within a brood, creating two family units. Recent theoretical work indicates that conflicts between individuals should select for brood division. However, little is known about the mechanisms involved in the onset and maintenance of this behavioural strategy. Given the high rate of fledglings’ begging calls, we hypothesized that acoustic discrimination could explain the stability of feeding preferences at a proximate level. In a 3-year field study, we recorded the responses of parent black redstarts, Phoenicurus ochruros, a territorial songbird, to playback of the begging calls of fledglings fed by the male and by the female. Parents responded more to the calls of the fledglings that they preferentially fed. A principal component analysis of the calls suggested that parents may recognize individual offspring. To our knowledge, this study provides the first evidence that a bird can acoustically discriminate between two categories of its own offspring: those that it preferentially feeds and those fed by the other parent.

Cooperative problem solving in African grey parrots ( Psittacus erithacus )

One of the main characteristics of human societies is the extensive degree of cooperation among individuals. Cooperation is an elaborate phenomenon, also found in non-human primates during laboratory studies and field observations of animal hunting behaviour, among other things. Some authors suggest that the pressures assumed to have favoured the emergence of social intelligence in primates are similar to those that may have permitted the emergence of complex cognitive abilities in some bird species such as corvids and psittacids. In the wild, parrots show cooperative behaviours such as bi-parental care and mobbing. In this study, we tested cooperative problem solving in African grey parrots (Psittacus erithacus). Our birds were tested using several experimental setups to explore the different levels of behavioural organisation between participants, differing in temporal and spatial complexity. In our experiments, African grey parrots were able to act simultaneously but mostly failed during the delay task, maybe because of a lack of inhibitory motor response. Confronted with the possibility to adapt their behaviour to the presence or absence of a partner, they showed that they were able to coordinate their actions. They also collaborated, acting complementarily in order to solve tasks, but they were not able to place themselves in the partner’s role.

Obtaining copulation solicitation displays in female canaries without estradiol implants

Female domesticated canaries (Serinus canaria) respond to conspecific song with copulation solicitation display (CSD) between 22 and 27 days after their first offspring has hatched. This period could be used to investigate the acoustical preferences of female canaries. This non-invasive method respects the natural reproductive cycle and could be an alternative to the invasive method of estradiol implants.

Urban noise undermines female sexual preferences for low-frequency songs in domestic canaries

Increasing levels of anthropogenic noise represent a challenge for animals living in urban areas and birds, especially, may suffer from noisy conditions as they use singing to attract mates. Most anthropogenic noise is low in frequency and singing at high frequencies under noisy urban conditions may avoid masking and thus be a good strategy for breeding success in cities. Despite comparative, correlational and some experimental studies supporting this hypothesis, empirical studies on the impact of noise on sexual behaviour are largely lacking. Domestic canaries, Serinus canaria, provide an excellent model system to test unequivocal sexual responsiveness as receptive females perform copulation solicitation displays (CSD) to male song. We have previously shown that CSD rate was higher for low- than for high-frequency songs. In the current study, we tested whether a typical urban noise spectrum, with a bias towards low frequencies, could undermine sexual preferences. Using overlapping and alternating noise exposure regimes while broadcasting male songs we found that masking by urban noise reduced female responsiveness to low-frequency attractive songs. Under the same conditions the responsiveness to high-frequency songs remained unaffected and, consequently, the sexual preference for low- over high-frequency songs had faded because of the urban noise. We discuss to what extent our results can be extrapolated to other wild bird species and speculate about the adaptive value of the typical upward shift in frequency found in many city birds.

Estimating the complexity of bird song by using capture-recapture approaches from community ecology

Repertoire size, the number of unique song or syllable types in the repertoire, is a widely used measure of song complexity in birds, but it is difficult to calculate this exactly in species with large repertoires. A new method of repertoire size estimation applies species richness estimation procedures from community ecology, but such capture-recapture approaches have not been much tested. Here, we establish standardized sampling schemes and estimation procedures using capture-recapture models for syllable repertoires from 18 bird species, and suggest how these may be used to tackle problems of repertoire estimation. Different models, with different assumptions regarding the heterogeneity of the use of syllable types, performed best for different species with different song organizations. For most species, models assuming heterogeneous probability of occurrence of syllables (so-called detection probability) were selected due to the presence of both rare and frequent syllables. Capture-recapture estimates of syllable repertoire size from our small sample did not differ significantly from previous estimates using larger samples of count data. However, the enumeration of syllables in 15 songs yielded significantly lower estimates than previous reports. Hence, heterogeneity in detection probability of syllables should be addressed when estimating repertoire size. This is neglected using simple enumeration procedures, but is taken into account when repertoire size is estimated by appropriate capture-recapture models adjusted for species-specific song organization characteristics. We suggest that such approaches, in combination with standardized sampling, should be applied in species with potentially large repertoire size. On the other hand, in species with small repertoire size and homogenous syllable usage, enumerations may be satisfactory. Although researchers often use repertoire size as a measure of song complexity, listeners to songs are unlikely to count entire repertoires and they may rely on other cues, such as syllable detection probability.

Parental care and brood division in a songbird, the black redstart

Sexual conflict over parental care can be mediated through differences in male and female overall feeding rates, brood division or both. At present, it is not clear whether post-fledging brood division occurs due to sexual conflict over parental investment or is due to bi-parental cooperation, e.g. increase offspring fitness. We provide evidence suggesting that brood division in the black redstart, Phoenicurus ochruros is due to sexual conflict. Males and females had similar feeding contributions during the nestling stage, which is common for most passerine species. After fledging, each parent showed long-term feeding preferences for particular chicks within the brood. In most cases (74%; 17/23) both parents provided care but males tended to feed less fledglings than females did and in about a quarter of cases (26%; 6/23) females fed the whole brood by themselves. The relative amount of male to female post-fledging feedings showed a significant negative relationship with the proportion of fledglings cared for exclusively by the male. These results suggest (1) a close link between the amount of parental care and brood division; (2) sexual conflict can be mediated through brood division; (3) female redstarts appear to loose this conflict more often than male redstarts, with in the extreme cases males showing post-fledging brood desertion. A literature review shows brood division to occur in at least a dozen of songbird species but male black redstarts have the lowest relative post-fledging parental investment, expressed either as feeding rates or number of chicks in care.

Preferences and Predispositions For Intra-syllabic Diversity in Female Canaries (Serinus Canaria)

The aim of this study is to examine the preferences of female canaries for a particular cue in male song: the intra-syllabic diversity (number and form of notes constituting a syllable) and to test both the role of predispositions and of song experience in the development of these preferences. Two groups of females were used. The first consisted of adult females raised in acoustic isolation without song males experiences (ISO group); the second, of song experienced adult females raised with singing male in an aviary (AVI group). Female preferences for intra-syllabic diversity were evaluated using the behavioral index of copulation solicitation displays (CSD). Five different types of songs were tested: three were made up of poor intra-syllabic diversity and two were made up of great intra-syllabic diversity. The results demonstrate that, in each group (AVI and ISO), intra-syllabic diversity is preferred to intrasyllabic simplicity. In addition, the inter-group comparison showed no significant differences between the two groups. In the aviary group, song learning by sexual and sound experience did not seem to modify or influence the intra-syllabic diversity preferences. Thus, female preferences for such a diversity would result from early predispositions that are maintained in adulthood.

Studying Female Reproductive Activities in Relation to Male Song: The Domestic Canary as a Model

Abstract Birdsong in oscine birds serves both intrasexual and intersexual functions. The aim of this chapter is to contribute to a better understanding of how birdsong is involved in female reproductive activity using the domestic canary as a model. Some special song phrases containing bipartite syllables composed of abrupt frequency falls and short silences (sexy phrases) appear to be particularly efficient to elicit sexual responses. Females canaries seem predisposed to prefer sexy phrases even though early or adult acoustic experience can affect this phenomenon. Moreover, eavesdropping on singing interactions, previous reproductive experience, as well as physical condition may be involved in shaping females’ preferences. Repeated exposures to male sexy phrases during reproduction do not influence the development of nest building or egg laying but affect egg quality. From the sender perspective, the production of the complex sexy phrases needs particular skills from the peripheral motor level as well as the central nervous system level.

SEXUAL RESPONSIVENESS OF FEMALE CANARIES TO SONG BOUT ORGANIZATION

Recent experiments demonstrated that in oscine species, 1) Some special sequences of multipartite songs convey more sexual information than others and 2) Stimulus change or switching is often associated with intersexual interactions. We looked for an influence of these two song cues in common domesticated canaries. Female canaries were tested for their sexual copulation solicitation display (CSD) in response to the playbacks of different strings of song sequences from males of the same breed. In order to induce habituation, three monotonous strings were created: A.A.A.A.A.A; B.B.B.B.B.B and C.C.C.C.C.C. (repetition of the same song sequence). In order to manage disrupt of habituation by stimulus changes, four types of strings including two types of song sequences were created: B.B.B.A.A.A., A.A.A.B.B.B., C.C.C.B.B.B. and B.B.B.C.C.C. We found that a monotonous repetition of the same sequence leads to habituation when the sexual potency of the sequence is high (sequences A and B) and that song sequences may greatly differ in eliciting sexual displays (A >B>C). Subsequent stimulus change may elicit an immediate response recovery. But such a disrupt of habituation occurs only if a prefered sequence follows a non prefered one. We discuss prominent parameters that may have influenced female sensitivity and responsiveness to string organization in domesticated canaries.