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Providing evidence to improve practice

Individual study: 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 intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Use aversive conditioning to reduce nest predation by avian predators Bird Conservation

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.