A new study from the Netherlands indicates that the increased usage of pesticides may be linked to the decline of the population of several species of birds.

The bird species, which are insect-eating birds, have their populations declining in areas in the Netherlands where the pesticides that are being used by farmers are the same ones that are suspected of causing the rapid decline of the population of bees.

The study, published in the Nature online scientific journal, was conducted by a team of scientists from the Radboud University in Nijmagen and the Dutch Centre for Field Ornithology and Birdlife Netherlands (SOVON). It reveals the first evidence that the pesticides in question, neonicotinoid pesticides, also have negative effects on larger creatures.

Among the birds that saw their population decline in certain parts of the Netherlands include starlings, barn swallows, tree sparrows and mistle thrushes. The study reveals that the pesticide also affects bird species by reducing or eliminating their insect prey.

"To our surprise we did find a very strong effect" on the bird species, said Caspar Hallmann of Radboud University who is the lead author of the study to Reuters. Out of the 15 bird species included in the study, nine of the, only feed on insects, while all 15 species only feed insects to their young.

"We cannot say this is proof (that the pesticide causes the decline in bird numbers) but we cannot explain the ... decline of birds by any other factors," added Hallmann, who also said that the study looked into several other possible reasons for the decline of the population of the bird species such as pollution.

The makers of the pesticides, however, deny that the products are causing the population decline.

"Neonicotinoids have gone through an extensive risk assessment which has shown that they are safe to the environment when used responsibly according to the label instructions," said a spokesman for Bayer, one of the manufactures of the pesticides.

"Birds living close to aquatic habitats -- the species that one could expect to be affected most by concentrations of neonicotinoids in surface water -- show no or negligible negative impact."

The European Union enforced a decision in April this year to impose a two-year moratorium on three types of neonicotinoids on flowering crops, due to the reported effects of the pesticide on the bee population, which are important for pollination. The pesticides, however, can still be used legally for non-flowering crops.