The development of personality: Age-related consistency of exploratory behaviour and gizzard size in red knots (Calidris canutus islandica)
Manche, P. (2017). The development of personality: Age-related consistency of exploratory behaviour and gizzard size in red knots (Calidris canutus islandica). MSc Thesis. NIOZ Royal Institute for Sea Research: Texel. 28 pp.
Animal personalities are defined as consistent between individual differences in behaviour across context and time. In adult red knots (Calidris canutus islandica), it was previously shown that exploratory behaviour differs consistently among individuals and that this behaviour is related to gizzard size in the field. To gain better understanding of the effect of ontogeny on the development of this aspect of personality, we studied adult and juvenile red knots in two successive years. Diet manipulations were used to change the gizzard size of the birds; low quality diet causes the gizzard size to increase, while high quality food results in a decrease. Measuring gizzard size and exploratory behaviour for a total of 8 times in two years, made it possible to study the mean differences between adults and juveniles as well as the development of these traits. When comparing overall means per age category, we found that juveniles had larger gizzards and were more explorative than adults. Exploratory behaviour was found to be already consistently different within individuals in both age classes during the first year of experiments, meaning that this is either genetically determined or becomes fixed within the first months of their lives. Gizzard mass was not significantly consistent within individuals. A correlation between gizzard mass and exploratory behaviour was not found, suggesting that in both adults and juveniles gizzard mass is driven by exploratory behaviour or correlated factors such as prey preference.
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