In 1972, Trivers’ landmark paper suggested that the current-future reproduction trade-off should lead to sexual conflict between parents, as each parent benefits when the other provides a greater share of the resources needed by offspring. Using this framework, many experimental and theoretical studies have since examined the outcome of sexual conflict over feeding decisions in bi-parental systems, at both evolutionary and behavioural time scales (Royle et al., 2013).

These studies have mostly focused on the amount of care that each parent delivers as a continuous variable, ignoring variation in the environment in order to maximise simplicity and generality. The realities of care are usually more complicated: in the case of offspring feeding behaviour parents often provide care to offspring in discrete units (e.g. food items), and offspring may benefit from both the consistency of care as well as the total amount of prey delivered. In addition, experimental and theoretical studies have demonstrated that coordinative behaviours between male and female partners during offspring provisioning existed, and could reduce the costs of sexual conflict. A positive relationship between turn-taking and total feeding rate in bi-parental systems has been found in bi-parental species (Johnstone et al., 2013, Bebbington & Hatchwell, 2015), showing that alternation might reduce the costs of sexual conflict for offspring and parents through a sort of policing mechanism (Axelrod & Hamilton, 1981; Trivers, 1971). Nest visit synchrony has also been documented in several species with bi-parental and cooperative care (Krebs et al., 1999; Masello et al., 2006; Lee et al., 2010). Synchronously visiting the nest can be adaptive by reducing predation risk for offspring (Raihani et al., 2010), by facilitating equal partitioning of food among nestlings fed simultaneously (Shen et al., 2010), or by improving assessment of chick need (McDonald et al., 2008). Synchrony at the nest has been associated with more regular feed visits, without involving a higher visit rate overall or greater equity between partners’ visit rates, but is associated with increased offspring mass and number in bi-parental species (Mariette & Griffith 2015).

These results suggest that in addition to feeding rate, studying consistency of care, and synchrony and alternation of parental visits might be crucial for understanding the outcome of sexual conflict. However it remains unclear how these parameters relate to each other or are modified by ecological conditions.

My PhD project aims to quantify the influence of multiple environmental parameters, social and non social, on offspsring feeding patterns, including coordinative behaviours, while raising young in Blue tits. A second goal of my study will be to identify and measure the environmental parameters that modulate behavioural responses of parents. The questions that will be addressed during this study are the following:

• What are the patterns of the feeding rate, including coordinative behaviours, of pairs in the studied populations?
• Whether this behaviour depends on external environmental variation?
• Do populations differ in parenting plasticity across an altitudinal gradient?

References

1. Trivers, R. L. (1971). The evolution of reciprocal altruism. The Quarterly review of biology 46, 35–57
2. Royle, N. J., Smiseth, P. T., and Kölliker, M. (2013). The evolution of parental care (Oxford University Press)
3. Johnstone, R. A., Manica, A., Fayet, A. L., Stoddard, M. C., Rodriguez-Gironés, M. A., and Hinde, C. A. (2013). Reciprocity and conditional cooperation between great tit parents. Behavioral Ecology 25, 216–222
4. Bebbington, K. and Hatchwell, B. J. (2015). Coordinated parental provisioning is related to feeding rate and reproductive success in a songbird. Behavioral Ecology 27, 652–659
5. Axelrod, R. and Hamilton, W. D. (1981). The evolution of cooperation. science 211, 1390–1396
6. Trivers, R. L. (1971). The evolution of reciprocal altruism. The Quarterly review of biology 46, 35–57
7. Krebs, E. A., Cunningham, R. B., and Donnelly, C. F. (1999). Complex patterns of food allocation in asynchronously hatching broods of crimson rosellas. Animal Behaviour 57, 753–763
8. Masello, J. F., Pagnossin, M. L., Sommer, C., and Quillfeldt, P. (2006). Population size, provisioning frequency, flock size and foraging range at the largest known colony of psittaciformes: the burrowing parrots of the north-eastern patagonian coastal cliffs. Emu-Austral Ornithology 106, 69–79
9. Lee, J.-W., Kim, H.-Y., and Hatchwell, B. J. (2010). Parental provisioning behaviour in a flock-living passerine, the vinous-throated parrotbill paradoxornis webbianus. Journal of Ornithology 151, 483–490
10. Raihani, N. J., Nelson-Flower, M. J., Moyes, K., Browning, L. E., and Ridley, A. R. (2010). Synchronous provisioning increases brood survival in cooperatively breeding pied babblers. Journal of Animal Ecology 79, 44–52
11. Shen, S.-F., Chen, H.-C., Vehrencamp, S. L., and Yuan, H.-W. (2010). Group provisioning limits sharing conflict among nestlings in joint-nesting taiwan yuhinas. Biology letters 6, 318–321
12. McDonald, P. G., Te Marvelde, L., Kazem, A. J., and Wright, J. (2008). Helping as a signal and the effect of a potential audience during provisioning visits in a cooperative bird. Animal Behaviour 75, 1319–1330
13. Mariette, M. M. and Griffith, S. C. (2015). The adaptive significance of provisioning and foraging coordination between breeding partners. The American Naturalist 185, 270–280