In central New Mexico, breeding populations of Bewick's wren (Thryomanes bewickii) recently colonized riparian forests of the Middle Rio Grande and have increased rapidly to become the sixth most abundant breeding bird species in bosque habitats. In 1997–1998, I studied the potential roles that cottonwood forest succession and alien plant species invasion might have had in facilitating this change in the distribution of the wren. Habitat preference and nest cavity limitation were examined at 12 sites near Albuquerque, New Mexico. Bewick's wrens nested only in native tree species, especially large cottonwoods (Populus deltoides). Territories defended by males had greater coverage of mature cottonwood and lower amounts of open, early successional habitats than areas not occupied by wrens. Analysis of wren abundance data from 70 sites throughout the Middle Rio Grande found wren abundance to be highest at sites dominated by cottonwoods, especially at sites having alien salt cedar (Tamarix chinensis) understories. However, at sites dominated by alien plant species, Bewick's wren abundance was low. When the number of suitable nest cavities was experimentally increased through provision of nest boxes, wren abundance increased and their distribution expanded, suggesting nest-site availability was a limiting factor in this population. The mature, even-aged cottonwood populations established around 1950 currently provide suitable conditions for breeding Bewick's wrens. However, the remarkable speed at which this species has increased suggests that other population factors might have affected its distribution and abundance.