Jon Atwood, PhD
Department of Environmental Studies
Interactions between the exotic invasive shrub Frangula alnus, glossy buckthorn, and its avian seed dispersers were studied at Ashuelot River Park in Keene, New Hampshire from July-September 2003. The objective of the study was to determine if a correlation exists between the timing of F.alnus fruit ripening and avian disperser abundance. Fruiting phenology was monitored throughout the season by recording the number of unripe, pre-ripe, and past-ripe berries on 30 fruiting F. alnus trees. Four species known to be F. alnus fruit dispersers were considered: American robin, cedar waxwing, European starling, and gray catbird. Avian abundance data was collected via weekly line transect surveys in two sections of the park defined as Open and Closed on the basis of general habitat structure. Analysis showed that numbers of European starling numbers were positively correlated with abundance of unripe and pre-ripe berries and negatively correlated with abundance of past-ripe berries over the entire study site. In the Open Area, gray catbirds were negatively correlated with the ripe berry abundance. None of the avian species showed significant, positive correlations with abundance of ripe berries throughout the study area.