Songbirds and Russian Olive Berries

Cedar Waxwings feeding on Russian olive berries

Yellow-rumped Warbler feeding on Russian olive berries

Currently, we are categorizing the berry production on selected Russian olive (exotic vegetation) and New Mexico olive (native vegetation) plants located on transects in our middle Rio Grande study area. The berries of these two plants provide an important food source for wintering (and to a lesser extend, migrating) birds that frequent the middle Rio Grande bosque. Russian olive berries are particularly important to wintering birds because they remain a viable food source throughout the winter or until the resource is depleted. In contrast, New Mexico berries tend to desiccate as winter progresses, and become a decreasingly useful food source. To date, we have documented over 30 bird species foraging on Russian olive berries, and a similar number exploiting New Mexico olive. Ultimately, we hope to generate a long-term berry production data set (10+ years) that can be compared to environmental conditions (i.e. weather patterns, river flow levels, etc.) to gain insight regarding factors that impact berry crop size in the middle Rio Grande bosque. -- written by Trevor Fetz, avian biologist