Fig. 4. Changes in the niche centre, amount of food consumed and
food properties between the short-term and long-term assays of food
preferences. The plots show the estimates and standard error of the
predicted responses of the model. The amount of total food, calories and
nutrients consumed is in grams. Results for PCoA 2 are shown in Fig. S3.
Unlike niche centre, niche breadth only changed between the short and
long-term assays in pigeons from MOIA (Fig. 5 ). In the
short-term assays, their WIC was smaller than that of individuals from
BCN and those raised in captivity. One year after, however, WIC had
expanded to levels similar to those of the other two groups. Although
individual niche expansion was also accompanied by an increase in
population niche breadth (WIC), the ratio WIC/TNW increased around 48%
from the short- to the long-term assays. This means that individuals
used a larger fraction of the resources exploited by the entire
population than they did one year before. While individuals from BCN and
those raised in captivity did not show similar niche expansions, the
ratio WIC/TNW also increased substantially as a result of a decrease in
the population niche breadth. Thus, the degree of resource
specialization within the population diminished over time.