Reduced Density and Nest Survival of Ground-Nesting Songbirds Relative to Earthworm Invasions in Northern Hardwood Forests

Scott R. Loss, Robert B. Blair

Research output: Contribution to journalArticlepeer-review

44 Scopus citations

Abstract

European earthworms (Lumbricus spp.) are spreading into previously earthworm-free forests in the United States and Canada and causing substantial changes, including homogenization of soil structure, removal of the litter layer, and reduction in arthropod abundance and species richness of understory plants. Whether these changes affect songbirds that nest and forage on the forest floor is unknown. In stands with and without earthworms in the Chequamegon-Nicolet National Forest, Wisconsin (U.S.A.), we surveyed for, monitored nests of, and measured attributes of habitat of Ovenbirds (Seiurus aurocapillus) and Hermit Thrushes (Catharus guttatus), both ground-dwelling songbirds, and we sampled earthworms at survey points and nests. Bird surveys indicated significantly lower densities of Ovenbirds and Hermit Thrushes in relation to Lumbricus invasions at survey point and stand extents (3.1 and 15-20 ha, respectively). Modeling of Ovenbird nest survival (i.e., the probability that nestlings successfully fledge) indicated that lower survival probabilities were associated with increased sedge cover and decreased litter depth, factors that are related to Lumbricus invasions, possibly due to reduced nest concealment or arthropod abundance. Our findings provide compelling evidence that earthworm invasions may be associated with local declines of forest songbird populations.

Original languageEnglish (US)
Pages (from-to)983-992
Number of pages10
JournalConservation Biology
Volume25
Issue number5
DOIs
StatePublished - Oct 2011

Keywords

  • Aves canoras neotropicales migratorias
  • Cascading effects
  • Catharus guttatus
  • Depredación de nidos
  • Efectos cascada
  • Hermit Thrush
  • Invasive earthworms
  • Lombrices de tierra invasoras
  • Neotropical migratory songbirds
  • Nest concealment
  • Nest predation
  • Ocultamiento de nidos
  • Ovenbird
  • Seiurus aurocapillus

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