In 1989, there was a large establishment of Penduline Tits in Kvismaren when nine individuals were present. The year after there was 14-21 individuals. Penduline Tit have a very exciting breeding biology and from the outset many individuals were colour-ringed. For such a small bird it is very mobile both within a breeding season and between years. It turned out that the Penduline Tits in central Sweden can be viewed as a single population. A male was moving for a few years between Köping, Kvismaren, Tåkern, Roxen and Venan! The species is both polygamous and polyandrous. This means that a female can breed with several males during a season and a male may breed with several females. Unfortunately the species has declined in recent years, not only at Kvismaren but in the whole of central Sweden.