The Economic Importance of Birds in Forests

1.The economic importance of birds in forests has been studied in many countries, but perhaps most intensively in Germany.This paper reviews our knowledge of the subject.2. Much information now exists on the composition of the insect food taken by forest species of birds and the amount they can eat in a stated period.But, although it has been shown that they devour large numbers of pest species, there is less information about what proportion of an insect population is removed by birds.There is evidence to suggest that this proportion does not increase when a plague develops.3. Methods of increasing the density of birds are discussed, particularly the provision of nest-boxes.It has been shown that, by careful siting, an unexpectedly large increase (from 5 to zo times) in density can be achieved.4. Evidence is given to show that birds can remove substantial proportions of insect pest populations when these populations are low.Their most important effect, therefore, may be in preventing a plague from developing rather than in reducing one that has already occurred.It is considered, therefore, that efforts to increase the densities of birds are far from being wasted.5. The protection of animals, such as bats and ants, which also eat plague species of insects, is advocated.*A review of the economic status of forest birds read at the conference on 'Birds and Forests' organised by the British Trust for Ornithology on 31 October 1959.