<p>Hur beter sig skärpiplärkor (Anthus petrosus) när de försvarar reviret mot en inkräktare under häckning? Eskalerar de aggressivitet olika eller har de en gemensam strategi? Påverkas beteendet av häckningsfas? Kan använd tid säga något om motivation att försvara revir? För att besvara dessa frågor placerades en burhållen artfrände av endera kön i etablerade revir. I studien mättes ägnad tid åt olika aggressiva beteenden, vilka hade klassats och graderats beroende av styrkan i hoten. Resultatet visade att alla hanar eskalerar aggression på ett likartat sätt och ägnade i medeltal lika lång tid åt olika nivåer. Individuella skillnader förekom dock då några individer eskalerade lite snabbare men det tolkades inte som ökad motivation att försvara revir. Tiden de ägnade åt de olika nivåerna varierade inte beroende av häckningsfas.</p> / <p>How do rock pipits (Anthus petrosus) behave when they defend a territory against an intruder during their breeding season? Do they escalate aggression differently, or do they have a common strategy? Does breeding phase influence the behavior? May used time tell something about the motivation to defend the territory? To answer these questions a caged conspecific of either sex were placed in established territories. In the study the time was measured of each different aggressive behavior, which had been classified into levels according to the intensity of the threat. The results showed that all males escalated aggression in the same way and devoted similar lengths of time to the different levels. Some individual differences occurred as a few individuals escalated somewhat rapidly, however, this was not interpreted as increased motivation to defend the territory. The time they devoted to different levels did not vary depending on breeding phase.</p>

Hur beter sig skärpiplärkor (Anthus petrosus) när de försvarar reviret mot en inkräktare under häckning? Eskalerar de aggressivitet olika eller har de en gemensam strategi? Påverkas beteendet av häckningsfas? Kan använd tid säga något om motivation att försvara revir? För att besvara dessa frågor placerades en burhållen artfrände av endera kön i etablerade revir. I studien mättes ägnad tid åt olika aggressiva beteenden, vilka hade klassats och graderats beroende av styrkan i hoten. Resultatet visade att alla hanar eskalerar aggression på ett likartat sätt och ägnade i medeltal lika lång tid åt olika nivåer. Individuella skillnader förekom dock då några individer eskalerade lite snabbare men det tolkades inte som ökad motivation att försvara revir. Tiden de ägnade åt de olika nivåerna varierade inte beroende av häckningsfas. / How do rock pipits (Anthus petrosus) behave when they defend a territory against an intruder during their breeding season? Do they escalate aggression differently, or do they have a common strategy? Does breeding phase influence the behavior? May used time tell something about the motivation to defend the territory? To answer these questions a caged conspecific of either sex were placed in established territories. In the study the time was measured of each different aggressive behavior, which had been classified into levels according to the intensity of the threat. The results showed that all males escalated aggression in the same way and devoted similar lengths of time to the different levels. Some individual differences occurred as a few individuals escalated somewhat rapidly, however, this was not interpreted as increased motivation to defend the territory. The time they devoted to different levels did not vary depending on breeding phase.

This study investigates the song-based recognition of individual songbirds with the main focus on the chiffchaff (Phylloscopus collybita) as a model species. The introductory part deals with vocalization-based recognition in birds in general.The following parts summarize our knowledge of individual recognition in songbirds based on song, namely the limitation of recognition ability caused by repertoire size or song sharing and how songbirds encode their identity in song. In the field study, we also proved the ability of the chiffchaff and willow warbler (Phylloscopus trochilus) to recognise particular neighbours based on one particular song from their repertoire. Our findings are interesting because chiffchaff and willow warbler differ in repertoire size and song organisation. We also analysed the repertoire size of chiffchaff males and the potential for identity encoding by basic voice characteristics (timing and frequency). We have found that chiffchaff song is unstable from year to year and that basic voice characteristics are useful for identification only when the same song type is used in the short time period. The last part of the thesis answers the question of whether there are some general voice characteristics independent of song content that might represent the structure of the sound organ and thus carry the identity of a bird independently of song content. We used ASRNI (Automatic system for the recognition of bird individuals) to identify particular birds based on unprocessed (raw) recordings of song without song preparation or manual measurements. This method also allows work with the data as an open set, so that the number of birds analysed does not have to be known in advance. Based on the parameters automatically extracted, we were able to recognise individuals with satisfactory accuracy. Based on such findings, we proved the existence of individually specific voice qualities that are independent of voice content and which may be used by birds for recognition. By using ASRNI we also introduced an approach that has great potential to be used in the effective acoustic monitoring of bird populations.