Individual acoustic monitoring based on individual differences in vocalizations is considered as promising tool that could substitute or complement traditional capture-mark individual tracking techniques at least for certain species of birds. In this lecture, we will give an example that capture-mark techniques may have long-term impact on a bird's behaviour (willow warblers avoid the second capturing even year after the first capture) and hence the development of non-invasive acoustic individual tracking techniques would be highly desirable. We will then continue by exploring the potential application of acoustic individual monitoring techniques in the two model bird species with fundamentally different vocalizations: little owl and chiffchaff. We will present the data on individual variation in calls and songs within and between years in both species and will discuss different practical issues associated with application of acoustic monitoring techniques: how many calls do we need to record, quality of recordings, which parameters should we focus on; size of the population that can be monitored, etc. We will argue that acoustic monitoring of songbirds is particularly challenging. Probably, analogues of content-independent speaker recognition methods will need to be used in many songbird species due to their complex and variable songs.