Bird use of saltcedar and cottonwood vegetation in the Middle Rio Grande Valley of New Mexico, U.S.A.

Riparian vegetation provides important habitat for migrating and breeding birds in the arid south-western United States. Surveys conducted in native cottonwood (Populus fremontii var. wislizeni) and introduced saltcedar (Tamarix chinensis) vegetation during spring, summer and fall were used to compare avian use of these two vegetation types along the Middle Rio Grande Valley in central New Mexico. Bird species richness in cottonwood and saltcedar did not differ during any season, but species composition varied. Overlap in species between the two habitats was lowest in spring and increased in fall, with more species unique to cottonwood than to saltcedar in all seasons. A number of obligate riparian species readily used saltcedar, while others were restricted to areas dominated by native vegetation. Neotropical migrants showed a slight preference for cottonwood in the spring, but some migrant species were detected in saltcedar as well, possibly reflecting the dense nature of this vegetation. However, although saltcedar was used by a number of species, maintenance of native vegetation will be necessary for the persistence of many bird species in the Middle Rio Grande Valley.