FACTORS INFLUENCING EXPANSION OF THE BREEDING DISTRIBUTION OF BEWICK'S WREN INTO RIPARIAN FORESTS OF THE RIO GRANDE IN CENTRAL NEW MEXICO

Abstract

Abstract 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) ...