Identifying individuals

In many studies, being able to identify individuals is essential. Focusing on the behaviour of an individual in a group is virtually impossible without a way of distinguishing reliably between one individual and another. Moreover, when differences in behaviour of known individuals are recorded, the resulting data are likely to be much more informative. Only by identifying and watching individuals does it become clear that all individuals in a species do not behave in the same ‘species-typical’ way.

In the laboratory, identification of individuals by rings, tags, collars, tattoo marks, painting the skin, dying feathers, fur-clipping and so forth does not usually offer major practical difficulties. However, it is important to realise that marking an individual may alter its behaviour or that of other individuals with which it interacts. To give one example, research revealed that coloured plastic leg bands placed on male zebra finches affected how attractive they were to members of the opposite sex. Female zebra finches preferred males wearing red leg bands over unbanded males, while males preferred females with black leg bands. Both males and females tended to avoid members of the opposite sex wearing green or blue leg bands (Burley, 2006). These findings clearly show that for zebra finches, and probably many other species, methods conventionally used to identify them can have a significant effect on behaviour.