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Invasive plants reduce number of bird songs

Roberta Kwok

Conservation This Week

Invasive plants could make forests a bit duller. According to a study in Ecology, birds that live in areas infested with weeds sing a smaller repertoire of songs.

The authors studied six sites in Lolo National Forest, Montana. Three were overrun by invasive spotted knapweed, and three were relatively unaffected by the infestation. In 2005 and 2006, the team surveyed chipping sparrows at each site and recorded their songs.

The infested sites had fewer native forbs and grasses and a lower proportion of older birds, the researchers report. Young birds typically mimicked their elders’ songs. The team detected an average of 9.2 songs per year at the sites with native plants, but only 7.6 songs at the invaded sites.

The results suggest that plant invasions “may erode song diversity,” the authors write. The yearlings have fewer old birds to learn from in these habitats, “resulting in increased similarity among songs and fewer song types overall.”