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How removal of invasive trees affects nesting birds in riparian areas

Date: August 24, 2015


Blue grosbeak is one of many bird species strongly tied to riparian areas in the Southwest (photo compliments of U.S. Fish & Wildlife Service).
Blue grosbeak is one of many bird species strongly tied to riparian areas in the Southwest (photo compliments of U.S. Fish & Wildlife Service).
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.

Key Findings

  • Along the Gila River, 95% of nests (100 of 105) were in native shrubs or trees. Only five nests were found in exotic vegetation, Russian olive (Elaeagnus angustifolia) or saltcedar.
  • Of 85 nests found along the Rio Grande, 54 (64%) were in saltcedar and 16 (19%) were in other non-native shrubs or trees.

  • Blue grosbeaks built their nests in plants of at least 20 species, but most (70%) nests were found in four native species of shrub or tree, primarily boxelder (Acer negundo), followed in order of decreasing frequency by seepwillow (Baccharis salicifolia), Goodding's willow (Salix gooddingii), and netleaf hackberry (Celtis reticulata).
  • 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.

  • When invasive exotic tree species were removed, riparian-nesting birds move into native trees and nest survival rates showed little change.


Featured Publications

Cartron, Jean-Luc E. ; Finch, Deborah M. ; Hawksworth, David L. ; Stoleson, Scott H. , 2013

Principal Investigators: 
Forest Service Partners: 
Scott H. Stoleson, Northern Research Station
Gila National Forest
External Partners: 
Jean-Luc E. Cartron, University of New Mexico
City of Albuquerque
Middle Rio Grande Conservancy District
Fish and Wildlife Service, Bosque del Apache National Wildlife Refuge
The Nature Conservancy
Phelps Dodge Corporation
U Bar Ranch
Joint Fire Science Program
Ducks Unlimited
New Mexico State Parks
U.S. Army Corps of Engineers
National Fish and Wildlife Foundation
Research Location: 
Central New Mexico's Middle Rio Grande corridor