Wintering populations of juncos at the UWM Field Station

Abstract

Since 1966 the winter populations of Dark-eyed Juncos, Junco hyemalis at the UWM Field Station have been monitored by mark-recapture methods. Schnabel estimates with 95% confidence intervals are presented for each winter. The population has varied irregularly between 60 and 196. Comparisons of these estimates with Wisconsin Christmas Bird Counts of juncos reveals a positive correlation with the average number of juncos per Wisconsin Christmas Bird Count, indicating that the year-to-year fluctuations at the Field Station correspond to the general state-wide fluctuations. However, the Christmas counts show a rising trend over the past 19 years while the Field Station population does not.