sentences:  A 2013 Dutch study found that water containing allowable concentrations of imidacloprid had 50% fewer invertebrate species compared with uncontaminated water.A later study found the analysis was confounded with other co-occurring insecticides and did not show imidacloprid directly affected invertebrate diversity.In the July 2014 issue of the journal "Nature", a study based on an observed correlation between declines in some bird populations and the use of neonicotinoid pesticides in the Netherlands demonstrated that the level of neonicotinoids detected in environmental samples correlated strongly with the decline in populations of insect-eating birds.