Biological links between personality and plasticity: testing some alternative hypotheses

When organisms respond behaviorally to a stimulus, they exhibit plasticity, but some individuals respond to the same stimulus consistently differently than others, thereby also exhibiting personality differences. Parent house sparrows express individual differences in how often they feed offspring and how that feeding rate changes with nestling age. Mean feeding rate and its slope with respect to nestling age were positively correlated at median nestling ages but not at hatching, indicating that individuality is primarily in plasticity. Individual differences could arise due to 1) interactions between environmental variables, 2) differences in underlying state or ‘quality’, or 3) differences in the ability to update cues of changing nestling demand. Individual slopes were modestly repeatable across breeding attempts, hinting at the likely action of additional environmental variables, but only brood size was important. I also found few correlates suggesting quality differences. I used sh..., Data were extracted from videos of marked adults at labelled nest sites. Videos were taken multiple times during the first 9 days of nestling development; most were of unmanipulated nests, but some nests were targetted for short-term (2 h) brood size manipulations. From the raw score sheets, several metrics, primarily the number of feeding visits and the length of the video, were extracted and entered into the data file. Additional information on the marked adults or the location and date of the video were added. Analysis was conducted in the R computing environment. , Saved as Excel.csv file, so openable by many programs.