Efficiency of conditioned aversion in reducing egg predation by breeding American crows Corvus brachyrhynchos along the Mississippi River border between Illinois and Iowa, USA

  • Published source details Dimmick C.R. & Nicolaus L.K. (1990) Efficiency of conditioned aversion in reducing depredation by crows. Journal of Applied Ecology, 27, 200-209


This study is summarised as evidence for the following.

Action Category

Use aversive conditioning to reduce nest predation by avian predators

Action Link
Bird Conservation
  1. Use aversive conditioning to reduce nest predation by avian predators

    A randomised, replicated and controlled before-and-after experiment at 21 sites in Illinois and Iowa, USA, in summer 1986 (Dimmick & Nicolaus 1990), found that predation of dyed-green chicken eggs by American crows Corvus brachyrhynchos over a 23 day period, was significantly reduced when 50% or 100% of green eggs (eight provided each day in total) were treated with Landrin (a tasteless but illness-inducing chemical). There was no corresponding reduction in consumption of green eggs at sites where they were not treated with Landrin. Sites where 12.5% of green eggs were treated had intermediate levels of predation (100% sites: 7.8 attacks/day before treatment vs. 1.2 attacks/day after provision of Landrin-treated eggs; 50% sites: 5.6 vs. 1.4; 12.5% sites: 6.0 vs. 3.4; control sites: 7.6 vs. 7.2). At 50% sites, crows also stopped predating un-dyed eggs and consumption was reduced at 12.5% and 100% sites but remained unchanged at control sites. Post-test trials (when green eggs were again distributed but did not contain Landrin) in 1986 found that crows resumed predation at 100% sites but not at 12.5% or 50% sites. Further tests in 1987 found that crows at all sites except 50% ones resumed predating green eggs.

Output references

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, terrestrial mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 18

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.

Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape Programme Red List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Bern wood Supporting Conservation Leaders National Biodiversity Network Sustainability Dashboard Frog Life The international journey of Conservation - Oryx British trust for ornithology Cool Farm Alliance UNEP AWFA Butterfly Conservation People trust for endangered species Vincet Wildlife Trust