Management & Land-Use Effects

Willow Riparian Grazing

The idea –

Although constituting less than one percent of western landscapes, riparian zones harbor the most species-rich avifauna of all the major habitats found in the western United States. Riparian areas are also the most modified land types in the West, with some estimates placing riparian habitat loss at greater than 95%. Grazing has also been identified as the major factor affecting riparian habitat quality in the western U.S. Thus, we designed a study to look specifically at the effects of the intensity of riparian grazing within the smaller willow-dominated streams in eastern Montana.

Methods –

We surveyed birds in about three dozen sites harboring tall (>2m) willow communities on east-side forests within USFS Region 1. Similarity levels from the USFS Riparian Implementation Guidelines for Grazing (USDA FS 1995) were used to assess grazing impacts, vegetative structure, and streamside conditions for the three comparative categories developed for this study. About a third of the sites had a history of heavy grazing, a third moderate grazing levels, and a third relatively little grazing, as reflected by structure.

Results –

Significant differences in vegetation structure were accompanied by significant changes in the probability of detection for several riparian-dependent bird species, suggesting that grazing effects are pronounced.