UK Tree Sparrow population crashed by 95% between 1974 and 1999

There has been a massive 95% decline in the UK Tree Sparrow Passer montanus population between 1974 and 1999. The nestling diet of Tree Sparrows is largely composed of invertebrates. It is possible that due to agricultural intensification in the late 20th century and increased use and effectiveness of insecticides there has been a decline in invertebrate prey, rendering large areas of farmland as suboptimal breeding habitat for Tree Sparrows.

Source: Field RH and Anderson GQA (2004) Ibis 146, 60-68
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