Upon reception, all birds were identified with a
coloured plastic leg band, and housed in single 43 cm × 53 cm × 30 cm cages. They had ad libitum access
to water and grit at all times, and to a commercial seed mix
for a minimum of 2 days. The birds were then weighed, and
the amount of food given to them was carefully controlled on
subsequent days to progressively bring all individuals down
to 85–90% of their ad libitum weight for the experimental
period. Once birds had reached their target deprivation
weight, testing began. Before each testing day, the subjects
were food deprived for 18 h overnight, and then moved from
the housing room to the experimental room where they were
given a 10 min habituation period. During all tests, the experimenter
was hidden behind a blind and observed the birds’
behaviours using a closed-circuit video system.