Effects of a habitat-altering invader on nesting sparrows: An ecological trap?

J. Cully Nordby, Andrew N. Cohen, Steven R. Beissinger

Research output: Contribution to journalArticlepeer-review

32 Scopus citations


Many invading species impact native species through predation, parasitism or competition, while others affect natives indirectly by restructuring their habitat. How invasive plants affect native animals, and to what extent native animals respond to changes in their habitat and the novel selection pressures that follow, is not well known. We investigated the impacts of a habitat-altering invader, the Atlantic cordgrass Spartina alterniflora, on the nesting success of Alameda song sparrows (Melospiza melodia pusillula), a California Species of Special Concern, in tidal marshes in three sites in San Francisco Bay. Date of laying was the most influential factor in determining daily survival rate of nests, but whether the nest was placed in exotic Spartina was the most important ecological variable. Nests placed in exotic Spartina had a success rate that was 30% lower than those placed in native vegetation. Nests in exotic Spartina were significantly more likely to fail due to tidal flooding than were nests placed in native vegetation, because the densest stands of exotic Spartina occurred at significantly lower elevations relative to the tides. Our results suggest that exotic Spartina may be an ecological trap for song sparrows in San Francisco Bay, attracting birds to nest sites that are often destroyed by tidal flooding.

Original languageEnglish
Pages (from-to)565-575
Number of pages11
JournalBiological Invasions
Issue number3
StatePublished - Mar 2009


  • Alameda song sparrow
  • Behavior
  • Ecological trap
  • Exotic species invasions
  • Invasive cordgrass
  • Melospiza melodia
  • Nest success
  • Spartina alterniflora
  • Tidal salt marsh


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