Invasive Prey Impacts the Abundance and Distribution of Native Predators

Abstract

While an extensive literature exists on the negative effects of invasive species, little is known about their facilitative effects on native species, particularly the role of invasives as trophic subsidies to native predators. The invasive gypsy moth (Lymantria dispar) undergoes periodic outbreaks during which it represents a super-abundant food source for predators capable of consuming it, particularly native cuckoos (Coccyzus erythropthalmus and C. americanus). We examined how gypsy moth outbreaks affect the abundance and distribution of cuckoos using the North American Breeding Bird Survey and 29 years of U.S. Forest Service gypsy moth defoliation records. Abundances of both Black-billed and Yellow-billed Cuckoos were significantly above average during outbreaks, but populations were average or below average in preceding and subsequent years, suggesting that cuckoos are immigrating to defoliations during outbreak years. Spatial analyses showed that cuckoo abundances approximately 40-150 km outside of defoliation areas were significantly below average, and these under-occupied breeding areas extended in all four compass directions around outbreaks. This result supports the idea that cuckoos locate gypsy moth outbreaks during a post-migratory nomadic phase. By shifting the annual distribution of cuckoos, gypsy moths may be shifting the trophic impact of cuckoos across large distances, which could affect native insect herbivores and plants.

Direct and indirect effects of alien insect herbivores on ecological processes and interactions in forests of eastern North America

“…that specialize on hairy caterpillars, and Barber et al (2008) observed a shift in cuckoo distributions during outbreaks, with more cuckoos in areas where gypsy moth was epidemic. As predators respond spatially and temporally to populations of alien insects, predation pressure on indigenous species may change in complex ways.…”

Citizen Science as an Ecological Research Tool: Challenges and Benefits

“…Similarly, Bonter et al (2009) did not detect population-level effects of the invasive Eurasian collared-dove on native Columbids in Florida. However, data from the North American BBS suggest that outbreaks of the invasive gypsy moth, Lymantria dispar, provide a trophic subsidy for some native bird species (Barber et al 2008).…”

Coqui frog invasions change invertebrate communities in Hawaii

“…Introduced species can change native communities by extirpating (Clavero and Garcia-Berthou 2005;Fritts and Rodda 1998), reducing (Lodge 1993;Porter and Savignano 1990;Sanders et al 2003), and even increasing native species (Barber et al 2008;Cohen and Carlton 1998;Roemer et al 2002). However, community-level changes induced by some non-natives can be difficult to observe, especially if the changes occur to communities that have high spatial and temporal variability, such as invertebrate communities.…”