Management Implications

Riparian systems associated with permanent water are very limited in the desert. However, washes, which are included in the preceding analysis, are more numerous. As we and others have shown, riparian habitats play a vital role in the desert ecosystem by providing water, food, and cover for resident and transient riparian birds, migrating birds, and non-riparian birds, such as quail and doves.

There are, in addition to the intensive use made of these high-value, low-quantity desert riparian systems by wildlife, numerous common high-intensity non-wildlife uses. For example, livestock and feral burros often congregate or linger in riparian habitats to take advantage of shade, forage, and drinking water. Recreationists are attracted to riparian systems in the desert by the shade and high visual quality. Washes are used as vehicular thoroughfares because they lack major obstacles. Mining operations frequently use the water associated with riparian systems in mining or mineral processing. They are also focal points of cultural resources, such as historic and native American sites.

Many of these uses are potentially in conflict with wildlife or maintenance of the riparian community. Riparian systems are generally recognized as vital to desert resident and migrant birds. Understanding the importance of riparian systems is vital to land managers as they attempt to resolve use conflicts. Resolution of these conflicts should take into consideration the breadth of resources which are critical to birds. Among these are the availability of surface water and the presence of a tree overstory and dense groundcover. Proper management should be aimed at maintaining or enhancing all of the individual components making up the riparian zone.

The geographic distribution of riparian systems should also be taken into account when assessing conflicts. Species such as Brown Towhee and Lazuli Bunting breed only in riparian vegetation in the Mojave and Great Basin deserts. Others, including Verdin, Abert's Towhee, and Black-tailed Gnatcatcher, generally are restricted to riparian systems in the Colorado Desert. An adequate distribution of well-managed riparian systems is essential, especially to the maintenance of species with limited distributions in the California deserts.

Results from biweekly surveys indicate that late December and early January is the time of lowest species richness (fig. 3) and bird abundance (fig. 4) at desert riparian sites. Winter bird-population studies conducted primarily in January and February show that midwinter to late winter species richness and abundance is higher. Thus, if it is necessary to create a disturbance such as building a fence or installing a management facility, construction during late December and early January is likely to have less of an impact than at other times. Of course, activities which damage habitat will be harmful to birds regardless of the season.

Human development and artificial habitats can be beneficial to the avifauna. Results of biweekly surveys (table 4) show that the two sites with the highest overall species occurrence (Old Woman Springs and Iron Mountain Pumping Station) are to a large degree man-made systems. Old Woman Springs (122 species recorded) includes a reservoir, residences, gardens, and ornamental trees mixed with native vegetation. Iron Mountain Pumping Station (121 species recorded) is an entirely artificial site with residential areas, parks, and a reservoir. These two sites were also especially high in number of year-round resident, fall migrant, and vagrant species. In addition to their structural diversity, with tall trees, buildings, dense shrubbery, and open water, these

sites were exceptionally large (36.4 ha. and 24.8 ha. respectively). Their low elevation (975 m. and 290 m. respectively) made both sites conducive to winter residents and winter transients. Thus, if properly mixed with native vegetation, artificial components can create structural diversity and provide nest and perch sites otherwise not available.

There are a few sites in the desert which are unusually rich in bird species. These frequently become focal points for birdwatchers (e.g., Morongo Valley, Furnace Creek Ranch). Such sites are normally large and diverse and support a substantial tree overstory. However, as knowledge of these sites increases, the importance of smaller, less well-known riparian sites can become obscured. Large sites have special management significance not only for the rarity of some of the birds found in them but also for the high level of public interest in their integrity. However, these sites and their contributions should not overshadow the importance of numerous other riparian sites and the contribution they make to supporting the desert avifauna.