Food-choice experiment
To assess food preferences of individuals, we presented each pigeon with
a six-section circular Plexiglas feeder containing 10g of six different
seed types (green peas, oats, popcorn maize, soybeans, sunflower seeds,
and wheat), an amount large enough to avoid being depleted during the
trial. The six food types were part of the diet of pigeons during the
acclimation period, and they were chosen to provide variation in size
and nutritional contents. Individuals were allowed to feed for 20
minutes. After this time, we removed the feeder and measured the amount
of each food remaining with a digital precision balance. The amount of
each seed type consumed per individual was estimated by subtracting this
quantity from the initial 10g. Trials in which an individual did not eat
were excluded from the analyses. To evaluate the consistency in the
measure, each individual was tested in a battery of 4 trials conducted
in two consecutive days. In the first daily trial, individuals were
tested under food-deprived conditions whereas in the second they had
already eaten. Thus, our experimental design allowed us to assess the
extent to which fasting influenced food choice (Moon & Zeigler 1979).
For some individuals (12 from MoiĆ , 14 from BCN and 28 raised in
captivity), long-term consistency in food preferences was evaluated by
repeating the food choice experiment a year later (two trials in one
day).