Importance of Native Understory for Bird and Butterfly Communities in a Riparian and Marsh Restoration Project on the Lower Colorado River, Arizona

Abstract

The riparian and marsh habitats of the lower Colorado River, Yuma, Arizona have been degraded by flow regulation, agricultural development, and non-native species invasion. Degradation has caused a decline in birds and butterfly communities. To improve habitat, restoration efforts have occurred at the Yuma East Wetlands (YEW), Arizona. In this study, we evaluated the effect of on-going riparian and marsh restoration on the community characteristics of breeding birds, butterflies, and vegetation, including cover, nectar resources, and host plant abundance at the YEW. Results indicated that restored riparian sites had four-fold higher total resident bird density than control habitats; however no difference was detected in riparian bird richness. Restored marsh habitats had two-fold higher total resident bird richness than the control habitats and three-fold higher marsh bird abundance than control habitats. Butterfly species richness and abundance were higher in restored riparian sites. Butterfly richness was correlated with flowering plant richness and abundance, vegetation species diversity, and percent herbaceous plant cover. Restored riparian sites had four times more total forb richness and abundance and five times higher host plant abundance than control riparian sites. Restored marshes had higher percent herbaceous plant cover and lower percent open water than control sites. This study indicates the importance of planting diverse native grasses and herbaceous plants and shrubs in restoration projects to benefit wildlife species.