Effects of Drought on Birds, Vegetation, and Surface Flow in a Desert Riparian Woodland

LaRoche, Dominic

Most climate projection models predict reduced water availability in southwestern North America within the next 100 years and a shift to a more arid climate. The reductions in available water from a changing environment, coupled with increasing water needs of growing human populations, will pose a substantial threat to desert riparian woodlands in future years. Riparian woodlands in the desert southwest provide habitat for many species of wintering, breeding, and migratory birds. Over 50% of breeding bird species in the southwest U.S. are thought to be dependent upon riparian woodlands even though these areas account for <1% of the landscape. Water, in the form of both ground water and surface water, is critical for maintaining healthy riparian woodlands. We conducted a longitudinal study of a riparian woodland in southeastern Arizona from 2006-2010 to determine how a riparian bird community responds to (and recovers from) drought effects, including decreased surface and ground water, increased plant mortality, and decreased plant cover. We surveyed birds and monitored nests while simultaneously measuring riparian vegetation, surface water, and ground water to track the changes in these variables resulting from a temporary drought. We documented declines in nesting attempts associated with the drought for three species of riparian birds. The presence of surface water was the most important predictor for 9 bird species and overall species richness. Other species responded to drought-induced changes in vegetation. Reductions in available water for desert riparian woodlands pose a substantial risk for many riparian-obligate bird species.

Effects of Drought on Birds, Vegetation, and Surface Flow in a Desert Riparian Woodland

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