Population dynamics of the Swedish Ornithological Society.

It has recently been recognized that there is declining interest in ornithology among the younger generations. In this paper we analyse the short and long-term dynamics of the Swedish Ornithological Society (SOF) and the Swedish Society for Nature Conservation (SNF) by using analytical tools from population ecology. We first show that the increasing number of SOF and SNF members is not the result of a constant proportion of ornithologists or people interested in nature conservation among a growing Swedish population. Hence, the number of members most likely reflects the true interest in joining organizations such as SOF. We also demonstrate that the growth rate of SOF can be fairly well estimated, but the possible equilibrium size is uncertain. Removing the long-term trend reveals a cyclic pattern with a period of 23 years. This pattern was not found when analysing the SNF data and we discuss the observed patterns in relation to human and member generation time. Finally, we present an improved population model based on data up to 1998 and show how model predictions compare with the observed number of members in year 2002.