A new research has warned the pesticides have been causing harm to many birds by eliminating insects that they survive on. Neonicotinoids have already been blamed for causing decline in the population of butterflies and bees, but it is the first time when a research has showed the contribution of pesticides in reducing the number of birds.

Results of the study, published in Nature, have been derived from analysis of bird population trends in the Netherlands from 2003 to 2010. Neonicotinoid was found to be common reason for the plight of insect-eating species like starlings, tree sparrows and swallows.

The high concentration of the chemical was found to be a key factor behind the decline. The research showed that concentrations of neonicotinoid more than 20 nanograms per liter cause an average of 3.5% reduction in the population of birds on an annual basis.

"We started with the bird population data and tried to explain the declines. Our study really makes the evidence complete that something is going on here. We can't go on like this anymore. It has to stop", said lead researcher Hans de Kroon, from Radboud University.

However, the findings of the study have been questioned by a spokesman for Bayer CropScience, which produces the chemical. He argued that an extensive assessment of the chemical has already proved that it is safe for the environment when used as per instructions on the label.

The results of the study have been referred as a wakeup call by Friends of the Earth Nature Campaigner Paul de Zylva. He suggested the UK government to pay heed to the findings of the study as bird population is already declining there.