In central New Mexico's Middle Rio Grande corridor, birds such as the blue grosbeak (Passerina caerulea), black-chinned hummingbird (Archilochus alexandri), and the endangered Southwestern willow flycatcher (Empidonax traillii extimus) nest in invasive exotic tree species. This dependency on otherwise undesirable invasive species raises concern about removing these exotic trees for wildfire control. However, if invasive trees are not removed and riparian woodlands burn, invasive tree species may replace important native species, which provide nesting sites for many species such as woodpeckers and hawks.
Researchers investigated this issue at the request of the Fish and Wildlife Service, the Middle Rio Grande Conservancy District, and the City of Albuquerque, NM. Researchers studied nesting success in areas dominated by native tree species such as willows (Salix spp.), areas dominated by invasive species such as tamarisk (Tamarix spp.), and areas where invasive trees were removed along the Gila and Rio Grande Rivers. The Rio Grande is a much more intensively managed ecosystem than the Gila River, with an understory dominated by saltcedar and other non-native invasive plants, frequent wildfires, and large-scale attempts at remediation of the vegetation.
Of 85 nests found along the Rio Grande, 54 (64%) were in saltcedar and 16 (19%) were in other non-native shrubs or trees.
Differences between the two sites in floristic composition and vegetation structure appeared to affect the placement of Blue Grosbeak nests more than they did nest success.