Are low-frequency songs sexually selected, and do they lose their potency in male–female interactions under noisy conditions?

ABSTRACT: We agree with Halfwerk et al. on the importance of including the receivers when studying the impact of anthropogenic noise. However, we find the conclusion that the use of lowfrequency song is sexually selected in great tits and that noisy conditions affect male–female communication premature for several reasons

Latitudinal distribution, migration, and testosterone levels in birds

Tropical bird species usually have lower testosterone (T) levels during breeding than temperate species. However, the potential mechanisms behind the positive interspecific correlation between T and latitude remain unexplored. In a comparative study of more than 100 bird species, we examined whether social constraints during male-male competition arising from migration and breeding synchrony are responsible for the latitude effects. Species that breed at higher latitudes are more likely to migrate and experience more intense intrasexual competition upon spring arrival than nonmigrant species from lower atitudes. Additionally, species from higher latitudes cope with shorter breeding seasons and thus with more synchronous breeding, which selects for high T titers via increased male-male conflicts. Accordingly, peak T levels were associated with migration and the duration of the egg laying period that reflects breeding synchrony. Because migration and breeding synchrony were related to latitudinal distribution, they appear to be important components of the latitude effects on T. A multivariate model controlling for covariation of predictor variables revealed that latitude remained the strongest predictor of peak T. Therefore, selection due to migration and breeding synchrony may partially cause the latitude effect, but other geographically varying factors may also play a role in mediating peak T levels at different latitudes

A link between eumelanism and calcium physiology in the barn owl.

In many animals, melanin-based coloration is strongly heritable and is largely insensitive to the environment and body condition. According to the handicap principle, such a trait may not reveal individual quality because the production of different melanin-based colorations often entails similar costs. However, a recent study showed that the production of eumelanin pigments requires relatively large amounts of calcium, potentially implying that melanin-based coloration is associated with physiological processes requiring calcium. If this is the case, eumelanism may be traded-off against other metabolic processes that require the same elements. We used a correlative approach to examine, for the first time, this proposition in the barn owl, a species in which individuals vary in the amount, size, and blackness of eumelanic spots. For this purpose, we measured calcium concentration in the left humerus of 85 dead owls. Results showed that the humeri of heavily spotted individuals had a higher concentration of calcium. This suggests either that plumage spottiness signals the ability to absorb calcium from the diet for both eumelanin production and storage in bones, or that lightly spotted individuals use more calcium for metabolic processes at the expense of calcium storage in bones. Our study supports the idea that eumelanin-based coloration is associated with a number of physiological processes requiring calcium

Neural Correlates of Experience-Induced Deficits in Learned Vocal Communication

Songbirds are one of the few vertebrate groups (including humans) that evolved the ability to learn vocalizations. During song learning, social interactions with adult models are crucial and young songbirds raised without direct contacts with adults typically produce abnormal songs showing phonological and syntactical deficits. This raises the question of what functional representation of their vocalizations such deprived animals develop. Here we show that young starlings that we raised without any direct contact with adults not only failed to differentiate starlings' typical song classes in their vocalizations but also failed to develop differential neural responses to these songs. These deficits appear to be linked to a failure to acquire songs' functions and may provide a model for abnormal development of communicative skills, including speech

Bonobo personality:Age and sex effects and links with behavior and dominance

Abstract The study described in this chapter examines whether individual differences in six rating-based bonobo personality dimensions—assertiveness, conscientiousness, openness, attentiveness, agreeableness and extroversion—are related to sex, age, behaviours and dominance. To these ends, the study tested predictions based on previous studies of human and chimpanzee personality, and bonobo behaviour and socio-ecology. Sex and age differences in assertiveness, openness and extroversion, and correlations between these personality dimensions and behaviour were consistent with predictions. Conscientiousness showed associations with observed behaviours but requires further investigation as sex and age effects differed from those reported in humans and chimpanzees. Agreeableness and attentiveness showed few associations with age, sex and behaviours, indicating the need to further investigate validity of these factors. This chapter shows that personality dimensions in bonobos are correlated with sex, age and behaviours in ways that are consistent with what is known for bonobos and their socio-ecology. L’étude décrite dans ce chapitre examine si les différences individuelles dans six dimensions de personnalité bonobos basées sur évaluation—Affirmation de soi, Conscience, Ouverture, Attention, Agréabilité, et l’Extroversion—sont liées au sexe et l’âge et les comportements et la dominance. L’étude a testé les prédictions basées sur des études précédentes de la personnalité humaine et chimpanzé, et le comportement bonobo et la socioécologie. Les différences de sexe et d’âge dans l’Affirmation de soi, l’Ouverture et l’Extroversion et les corrélations entre ces dimensions de personnalité et de comportement étaient cohérents avec nos prédictions. La Conscience montre des associations avec les comportements observés mais a besoin plus de recherche vu que les effets du sexe et de l’âge diffèrent des effets rapportés chez les humains et les chimpanzés. L’Agréabilité et l’Attention n’avaient pas autant d’associations avec l’âge, le sexe et les comportements. Cela montre qu’il faut plus rechercher la validité de ces facteurs. Cette étude montre que les dimensions de personnalité chez les bonobos sont corrélé à l’âge, au sexe et aux comportements de manières qui sont cohérentes avec notre connaissance des bonobos et de leur socioécologie.</jats:p

Effects of experimentally sustained elevated testosterone on incubation behaviour and reproductive success in female great tits (Pants major)

n many seasonally breeding birds, female and male testosterone (T) levels peak at the start of the breeding season, coinciding with pair bonding and nesting activities. Shortly after the onset of egg laying, T levels slowly decline to baseline levels in both sexes, but more rapidly so in females. During this period, T in males may still function to facilitate territorial behaviour, mate guarding and extra pair copulations, either via short lasting peaks or elevated basal levels of the hormone. In some species, however, males become insensitive to increased T after the onset of egg laying. It has been postulated that in these species bi-parental care is essential for offspring survival, as T is known to inhibit paternal care. However, only very few studies have analysed this for females. As females are heavily involved in parental care, they too might become insensitive to T after egg laying. Alternatively, because territorial defence, mate guarding and extra pair copulations are expected to be less important for females than for males, they may not have had the need to evolve a mechanism to become insensitive to T during the period of maternal care, because their natural T levels are never elevated during this part of the breeding season anyway. We tested these alternative hypotheses in female great tits (Parus major). Male great tits have previously been shown to be insensitive to T after egg laying with regard to nestling feeding behaviour (but not song rate). When females had started nest building, we experimentally elevated their T levels up to the nestling feeding phase, and measured incubation behaviour (only females incubate) and reproductive success. T did not significantly affect nest building or egg laying behaviour, although egg laying tended to be delayed in T females. Females with experimentally enhanced T maintained lower temperature during incubation but did not spend less time incubating. This might explain the reduced hatching success of their eggs, smaller brood size and lower number of fledglings we found in this study. As in this species T-dependent behaviour by females during the phase of parental care is not needed, the results support the hypothesis that in this species the need for selection in favour of T-insensitivity did not occur