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).