Classification 3: Mimickery

The purpose of this trial was to determine how well a neural network would respond to a recording of a mimicked vocalization. Starlings have a wide range of vocalizations including those learned from other birds. Among the vocalizations commonly mimicked by the Starling are those of large birds of prey. It is thought that they do this in order to scare other small birds away from their territories. The basic network was built and trained against both European Starlings own vocalizations and those of Bald Eagles. The network perfectly classified both calls when tested. Finally, a recording of a Starling mimicking the Bald Eagle call used for training was passed into the network. The following figure shows the frequency spectrum of typical Starling and Bald Eagle vocalizations as well as that of the mimicked vocalization passed into the network.

While the network classified the mimicked vocalization as a Bald Eagle in almost all networks built, the numeric result produced showed that the decision was a close one. While the typical Starling and Eagle vocalizations were given values close to one for the correct category, and values close to zero for the incorrect category, the mimicked vocalization was given a value between 0.5 and 0.6 for the Eagle category and 0.4 to 0.5 for the Starling category in most cases. This shows that, while the network could not classify the mimic as a Starling, it didn't fit the classification of Eagle much better.