Results
The proportion of time spent by individual birds on a sapling was
dependent of the combination of saplings, bird training, and significant
interaction of both factors (X2 = 31.62, P = 0.001).
This result suggests that the difference between experiments is
dependent of the type of training given to the individual bird.
Naïve birds (control) spent around 50% of their time on each of the two
saplings in four out of the five experiments (Fig. 1; Table S1). Elm
trained birds spent significantly longer time on induced elm saplings
than noninduced elm saplings (Figure 1). The time spent on each sapling
varied significantly across experiments (Table 2). In experiments where
herbivore induced elm saplings were presented with noninduced elm
control (Exp 1) or noninduced guava (Exp 3), birds spent respectively
82% (69% to 91%) and 75% (58% to 87%) of their time on the induced
saplings. In experiment 2, 4, and 5 birds spent equal amount of time on
each treatment (Figure 1). When induced elm saplings were presented with
induced guava saplings in experiment 2, birds only spent c. 56% (25%
to 64%) on induced elm. Experiments 4 and 5 did not contain induced elm
samplings, but contained induced guava sapling, but the birds did not
show any specific preference (Figure 1, Table S2).
Guava trained birds spent significantly higher amount of time on
herbivore induced saplings than non-induced saplings (Figure 1). The
time spent on each sapling varied significantly across experiments
(Table S3). In experiments 4 and 5, where herbivore induced saplings
were presented with non-induced saplings, birds spent c. 82% (67% to
91%) and 76% (58% to 88%) of their time on those saplings. In
experiment 2, where herbivore induced guava saplings were presented with
herbivore induced elm sapling, birds spent c. 71% (52% to 85%) of
their time on induced guava saplings. In experiments 1 and 3 where
herbivore induced elm saplings were presented, birds did not show any
specific preference (Figure 1).