Wednesday, October 7, 2009

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

Monday, October 5, 2009

Raptors of the Rio Grande Gorge

This Golden Eagle nestling fledged prematurely. However, it still has a good chance of survival because of its large size, and because its parents will continue to provide care while it is on the ground.
Golden Eagles continue to add to existing nests for many years, eventually amassing a massive structure several feet tall and several feet wide.

There is a fissure, a crack of basalt that runs through north central New Mexico. In it lies a river, the hydrologic aorta of the state, the Rio Grande. Within this canyon nesting Golden Eagles thrive, along with Prairie Falcons, and Red-tailed Hawks. Commonly known as the Rio Grande Gorge, it contains some of the largest Golden Eagle nests that I have ever seen. Some of which attain heights nearing 10 feet, attesting to fact that Golden Eagles have been using these nest sites in the gorge for a very, very, long time.

Written by Ron Kellermueller, raptor biologist