Effect of motivational context on conspecific song discrimination by brown-headed cowbirds (Molothrus ater)

Whistle discrimination and categorization by the Atlantic bottlenose dolphin (Tursiops truncatus): a review of the signature whistle framework and a perceptual test

Dolphin whistles vary by frequency contour, changes in frequency over time. Individual dolphins may broadcast their identities via uniquely contoured whistles, "signature whistles." A recent debate concerning categorization of these whistles has highlighted the on-going need for perceptual studies of whistles by dolphins. This article reviews research on dolphin whistles as well as presenting a study in which a captive, female, adult bottlenose dolphin performed a conditional matching task in which whistles produced by six wild dolphins in Sarasota Bay were each paired with surrogate producers, specific objects/places. The dolphin subject also categorized unfamiliar exemplars produced by the whistlers represented by the original stimuli. The dolphin successfully discriminated among the group of whistles, associated them with surrogate producers, grouped new exemplars of the same dolphin's whistle together when the contour was intact, and discriminated among same-contour whistles produced by the same dolphin. Whistle sequences that included partial contours were not categorized with the original whistlers. Categorization appeared to be based on contour rather than specific acoustic parameters or voice cues. These findings are consistent with the perceptual tenets associated with the signature whistle framework which suggests that dolphins use individualized whistle contours for identification of known conspecifics.

Cities Change the Songs of Birds

Worldwide urbanization and the ongoing rise of urban noise levels form a major threat to living conditions in and around cities. Urban environments typically homogenize animal communities, and this results, for example, in the same few bird species' being found everywhere. Insight into the behavioral strategies of the urban survivors may explain the sensitivity of other species to urban selection pressures. Here, we show that songs that are important to mate attraction and territory defense have significantly diverged in great tits (Parus major), a very successful urban species. Urban songs were shorter and sung faster than songs in forests, and often concerned atypical song types. Furthermore, we found consistently higher minimum frequencies in ten out of ten city-forest comparisons from London to Prague and from Amsterdam to Paris. Anthropogenic noise is most likely a dominant factor driving these dramatic changes. These data provide the most consistent evidence supporting the acoustic-adaptation hypothesis since it was postulated in the early seventies. At the same time, they reveal a behavioral plasticity that may be key to urban success and the lack of which may explain detrimental effects on bird communities that live in noisy urbanized areas or along highways.

Sexual equality in zebra finch song preference: evidence for a dissociation between song recognition and production learning

Song in oscine birds is a culturally inherited mating signal and sexually dimorphic. From differences in song production learning, sex differences in song recognition learning have been inferred but rarely put to a stringent test. In zebra finches, Taeniopygia guttata, females never sing and the species has one of the greatest neuroanatomical differences in song-related brain nuclei reported for songbirds. Preference tests with sibling groups for which exposure to song had been identical during the sensitive phase for song learning in males, revealed equally strong influence of the tutor's song (here the father) on males' and females' adult song preferences. Both sexes significantly preferred the father's over unfamiliar song when having free control over exposure to playbacks via an operant task. The sibling comparisons suggest that this preference developed independently of the song's absolute quality: variation between siblings was as great as between nests. The results show that early exposure has an equally strong influence on males' and females' song preferences despite the sexual asymmetry in song production learning. This suggests that the trajectory for song recognition learning is independent of the one for song production learning.

Self-referent phenotype matching: theoretical considerations and empirical evidence

In most birds and mammals, young are raised in family groups. The phenotypes of nestmates and parents are thus reliable cues for recognition of conspecifics and kin. However, in some species, young develop alone, or in broods of mixed relatedness (e.g. because of multiple paternity or maternity), or among heterospecifics or unrelated conspecifics (brood parasites). Under these circumstances, the best referent (model) for discriminating close from distant kin and heterospecifics from conspecifics might be one's own self. This recognition process is known as self-referent phenotype matching. Here we review recent experimental evidence of self-referencing and suggest that behavioral neuroscience can provide new tools and insights into how it works (its proximate mechanistic and ontogenetic bases) and why it exists (its adaptive significance).

Perceptual salience of individually distinctive features in the calls of adult king penguins

In the king penguin, Aptenodytes patagonicus, incubation and brooding duties are undertaken alternately by both partners of a pair. Birds returning from foraging at sea find their mate in the crowded colony using acoustic signals. Acoustic recognition of the mate maintains and strengthens the mate's fidelity and favors synchronization in the different stages of reproduction. In this study it was found that the king penguin vocalizes in response to the mate's playback calls, but not to those of neighbors or unfamiliar conspecific individuals. To study individual features used by the birds for individual recognition of mates, various experimental signals consisting of synthesized modifications of the mate' s call were played back to the incubating bird. Results indicated that birds attend to the FM profile of the call, in particular its initial inflexion. The frequency modulation shape of the syllable can be assimilated to a vocal signature repeated though the different syllables of the call. King penguins pay little attention to the call' s AM envelope or its absolute frequency.

Stronger territorial responses to frequency modulated coos in collared doves

Playback experiments were used to investigate the perception of frequency variations in perch coos by collared doves, Streptopelia decaoctoTerritorial males responded more strongly to modulated than to unmodulated coos. This effect was seen whether all three elements of the coo, or just the first element, were modulated. Modulated coos differed from unmodulated coos in two ways, first by an increased average frequency, and second, by the presence of a discrete change in frequency. We show that it was the change in frequency that was responsible for the level of response to modulated coos. The stronger responses to modulated coos are interpreted as a result of the receiver rating the sender as a stronger competitor.Copyright 1997 The Association for the Study of Animal Behaviour1997The Association for the Study of Animal Behaviour