Avian sex allocation and ornamental coloration:A study on blue tits

Korsten P. Avian sex allocation and ornamental coloration: a study on blue tits.; 2006

Repeatable parental risk taking across manipulated levels of predation threat:No individual variation in plasticity

Salazar S, Hlebowicz K, Komdeur J, Korsten P. Repeatable parental risk taking across manipulated levels of predation threat: no individual variation in plasticity. Animal Behaviour. 2023;196:127-149.Individuals respond adaptively to their environment. Yet, they may differ in their responses even when confronted with the same environmental challenge. Several complementary conceptual frameworks suggest that within populations among-individual variation in life history strategies aligns not only with individuals' propensities to take risks across different situations but also with their sensitivity to variation in environmental cues. Risk-prone individuals, suggested to invest more in current reproduction at the cost of their future reproductive prospects, are predicted to be less sensitive to environmental variation than risk-averse individuals. We tested this prediction in a population of breeding blue tits, _Cyanistes caeruleus_, by confronting them with different levels of predation threat at their nests and recording their latency to resume brood provisioning after the removal of the predator stimulus. We presented taxidermic woodpecker, _Dendrocopos major_ (a common brood predator) and sparrowhawk, _Accipiter nisus_ (a common adult predator) mounts at each nest, respectively representing low and high levels of threat to adult blue tits. As a nonpredator control stimulus, we presented a blackbird, _Turdus merula_, mount. We found that on average parents took longer to resume provisioning after presentation of a sparrowhawk than a woodpecker or blackbird. Furthermore, individual latency responses across all threat levels taken together were repeatable. However, despite the population level plastic adjustment to the level of predation threat, we found no evidence for among-individual variation in plasticity. Instead, individual differences in responses were roughly maintained across all levels of threat. While our findings show that individuals differ in their level of risk taking, in the high-stakes and ecologically relevant context of predation risk during parental care, commonly held expectations about among-individual variation in behavioural plasticity were not met

Chemical analysis reveals sex differences in the preen gland secretion of breeding Blue Tits

Caspers B, Marfull R, Dannenhaus T, Komdeur J, Korsten P. Chemical analysis reveals sex differences in the preen gland secretion of breeding Blue Tits. Journal of Ornithology. 2021;163(1):191–198.**Abstract** Acoustic and visual signals are well known to play important roles in social communication in birds. Growing evidence suggests that many bird species, including species of songbirds, additionally have a well-developed sense of smell. However, we are still at the beginning of understanding the potential importance of chemical communication in the social lives of birds, for example in mate choice. The secretion of the preen gland may be an important contributor to the chemical phenotype of birds. Here, we report on a first characterisation of the chemical composition of the preen gland secretion of the Blue Tit (Cyanistes caeruleus), a common songbird which is an often used model species in animal behaviour and ecology, in particular also in studies of sexual selection and (extra-pair) mate choice. We found sex differences in the composition of the preen gland secretion in breeding Blue Tits. Females further tended to have a larger number of putative compounds in their secretions compared to males. We briefly discuss the possible implications of these findings and speculate that the chemical composition of the preen gland secretion may be a sexually selected trait in Blue Tits. Our preliminary findings warrant follow-up research into the patterns of within- and among individual variation in the chemical composition of the preen gland secretion as well as the identification of the main chemical compounds involved.**Zusammenfassung**Chemische Analyse zeigt Geschlechtsunterschiede im Bürzeldrüsensekret brütender BlaumeisenSingvögel sind vor allem für ihren Gesang und ihre Gefiedermerkmale, die bei der sozialen Kommunikation eine bedeutende Rolle spielen, bekannt. Immer mehr Hinweise deuten aber darauf hin, dass viele Vogelarten, darunter auch Singvogelarten, zusätzlich einen gut entwickelten Geruchssinn haben. Welche Bedeutung die geruchliche Kommunikation im sozialen Leben der Vögel, zum Beispiel bei der Partnerwahl, spielt ist allerdings weitgehend noch unbekannt. Das Bürzeldrüsensekret könnte in diesem Zusammenhang einen wichtigen Beitrag zum chemischen Phänotyp der Vögel leisten. In unserer Studie haben wir uns die chemische Zusammensetzung des Bürzeldrüsensekrets der Blaumeise (Cyanistes caeruleus) in der Brutzeit angeschaut. Blaumeisen sind eine viel genutzte Modellart in der Verhaltensforschung und Verhaltensökologie, insbesondere auch in Studien zur sexuellen Selektion und (außerpaarigen) Partnerwahl. Anhand von chemischen Analysen mittels Gas-Chromatographie fanden wir heraus, dass es bei brütenden Blaumeisen einen Geschlechtsunterschied in der Zusammensetzung des Bürzeldrüsensekrets gibt. Weibchen neigen außerdem dazu, eine größere Anzahl von vermeintlichen Substanzen in ihren Sekreten zu haben als Männchen. Wir diskutieren hier kurz die möglichen Implikationen dieser Ergebnisse und spekulieren, dass die chemische Zusammensetzung des Bürzeldrüsensekrets ein sexuell selektiertes Merkmal bei Blaumeisen sein könnte. Unsere vorläufigen Ergebnisse rechtfertigen Folgeuntersuchungen, in denen die Identifikation der wichtigsten chemischen Verbindungen des Bürzeldrüsensekrets und die Variation innerhalb und zwischen Individuen in der chemischen Zusammensetzung des Drüsensekrets im Fokus stehen

Sexual conflict in twins: male co-twins reduce fitness of female Soay sheep

Males and females often have different requirements during early development, leading to sex-specific interactions between developing offspring. In polytocous mammals, competition for limited resources in utero may be asymmetrical between the sexes, and androgens produced by male foetuses could have adverse effects on the development of females, with potentially long-lasting consequences. We show here, in an unmanaged population of Soay sheep, that female lambs with a male co-twin have reduced birth weight relative to those with a female co-twin, while there was no such effect in male twins. In addition, females with a male co-twin had lower lifetime breeding success, which appeared to be mainly driven by differences in first-year survival. These results show that sex-specific sibling interactions can have long-term consequences for survival and reproduction, with potentially important implications for optimal sex allocation