Optimisation of parental effort: state dependent parental care strategies in birds
Final Report Abstract
Parents should adjust parental care flexibly to variations in parental and offspring condition – and in species with biparenal to partner condition to maximize lifetime reproductive success. I here investigated the effect of reduced female condition as nest attendance behaviour in an experimental field study in lesser black-backed gulls on male parental care. Conflict theory poses that for biparental care to be stable partners should only partially compensate. However, in gulls predation risks can be high and partial compensation may not be an option. Accordingly, males in this study showed completely compensated for reduced female effort. I am also interested in the understanding of proximate mechanisms that mediate adjustments in parental care. They are poorly understood, yet may help to understand the constraints within which adjustments in parental behaviour can occur. Plasma prolactin is known to be elevated during parental care, however, it is not clear if it is a mere prerequisite for parental behaviour or if it is involved in adjustments in parental behaviour. I did not find any relationship between the nest attendance behaviour of female lesser black-backed gulls and prolactin levels. In zebra finches, I investigated the interactions between parents and their offspring. Conflict theory predicts a conflict between parents and offspring over the amount and duration of the parental care period. The outcome of this conflict may depend on parental sensitivity to variation in offspring state. We examined if parents continue parental care for a fixed time period of are sensitive to offspring age by cross-fostering chicks of different ages. Zebra finch parents were very responsive to changes in offspring need and prolonged or shortened the care period according to the age of their foster chicks. All chicks fledged and became independent at the same age. Our results on provisioning behaviour at different stages of the car period suggest that parental sensitivity to offspring needs varies over the care period, with parents being more responsive to chick needs in the early parental care period, probably because costs of underestimating offspring needs are particularly high when chicks are very young and decrease over the course of the care period with increasing chick independence.
Publications
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2012 Flexibility in the duration of parental care: zebra finch parents respond to offspring needs, Animal Behaviour 83, 35-39
Rehling, A., Spiller, I., Krause,, E. T., Nager, R. G., Monaghan, P. & Trillmich, F.
