Trends in avian community structure across a gradient of native to invasive riparian vegetation in northwest New Mexico

In riparian areas of the arid and semi-arid western North America, tamarisk (Tamarix spp.) and Russian olive (Elaegnus angustofolia ) threaten native cottonwood (Populus fremontii) and willow (Salix spp.) habitats. Although resource managers are actively managing these invasive species, the effects of these invasives on bird communities are site and species specific. Why some species, guilds, and families do poorly and others are either unaffected or thrive in the face of invasion is poorly understood. On the San Juan and Animas Rivers in northwest New Mexico, I used point count surveys, vegetation assessments, and prey surveys to address how avian communities, species, guilds, and groups respond to a gradient of native to invasive riparian vegetation and which life history characteristics make them predisposed to avoidance or attraction to invasive vegetation types. Sites containing predominantly native vegetation had higher avian and invertebrate species richness and diversity than predominantly invasive sites, but avian species did not respond uniformly to the gradient. My results suggest that responses to the vegetation gradient are species-specific and have practical management implications.