Spectacled parrotlets live in a complex system of social relationships. Soon after fledging the young establish close sibling relationships. These sibling groups are stable for more than a year and may be re-established in case of mate loss. After a period of indifferent relations either with their siblings or with unrelated individuals of the opposite sex the pair bond becomes the central unit of the parrot's social network. In a series of playback experiments we tested the importance of contact calls for individual recognition within this social network. The experiments showed that:
- adult spectacled parrotlets could differentiate between the contact calls of their pair mates and those of other group members,
- juveniles are able to differentiate between the contact calls of their siblings and those of other group members, and
- soon after pair bond formation paired individuals show affiliative interactions exclusively with their mates but keep in acoustic contact with their siblings.
It is proposed that contact calls are important for individual recognition of siblings, pair mates and group members in spectacled parrotlets. Individual recognition by contact calls is an important mechanism for the formation of sibling groups and pair bonds. The maintenance of acoustic contact with siblings after pair bond formation facilitates the re-establishment of sibling relationships in case of mate loss.