Where have all the birds gone?
RSPB report blames pesticides

A new report from the Royal Society for the Protection of Birds (RSPB) shows that an alarming number of bird populations have crashed in the last twenty five years-and pesticides are implicated as one of the main causes. Rachel Carson's seminal work Silent Spring, on the same theme, was written well over thirty years ago. How long can we continue using pesticides in this way? Peter Beaumont reports on the main findings.

Tree sparrow 89% population decline

Reed bunting 61% population decline

Swallow 43% population decline

Starling 23% population decline

The new RSPB report(1) links the use of pesticides with declining populations in a number of bird species. The Indirect Effect of Pesticides on Birds was commissioned by the Department of the Environment, produced by the Joint Nature Conservation Committee (JNCC) and edited by English Nature and RSPB. It focuses on three ways that pesticides could affect birds:

• insecticides may reduce the abundance of invertebrates, an important food source during the breeding season;

• herbicides may reduce the number of host plants, reducing the numbers of invertebrates that depend on them;

• herbicides may also reduce the abundance of weeds and seeds which provide food for birds in winter, and some species during breeding.

Link with pesticides
Dr Andy Brown, JNCC Chief Officer said "The public and conservation bodies have been hearing about the declining numbers of some of our most familiar birds with rising concern. It has become clear that one of the more likely causes has been identified: the effects of pesticides, which are eliminating the birds' food supply."
    Other changes in agriculture may also have contributed to declining populations-such as silage making instead of hay making (removing food and cover for bird and insect populations earlier in the season) and winter cropping (involving pre-emergent herbicide use to 'clean' fields and reducing over-wintering habitats). Nevertheless the decline in birds is linked to an increase in the frequency of pesticide use in cereals (measured by application frequency) of nearly three times over the same 25 year period.

Recommended changes to agricultural practice 

• The adoption of Integrated Crop Management and an agri-environment scheme that sets a targeted reduction of pesticide use;

• a switch to organic farming;

• better monitoring of invertebrates and plants;

• more research on the ecology of individual bird species;

• large scale experimental studies assessing the effects of pesticides and other agricultural factors on wildlife.

Pesticides Trust [now PAN UK] comment
It is not clear that the recommended changes to current agricultural practice will be enough. Most of the decline appears to be due to the legitimate use of pesticides, according to label directions. In this context, no one is accusing farmers of misuse. The reduction in use will need to be drastic to reduce the decline in bird populations-is it likely that simply better use of pesticides will achieve this? Integrated crop management (ICM) does not itself call for a reduction in use of pesticides-certainly not when compared with organic farming.
    Although there have been helpful developments in crop management to encourage diversity and habitats and food for bird populations, such as beetle banks and conservation headlands, these will not be of great benefit in very large cereal fields.
    It is now time to consider a tax on pesticide use, and severe restriction on targeted products that may have most effects on biodiversity-broad spectrum organophosphate insecticides.

Urgent questions now need answers

• Can populations recover from such crashes?

• What are the indirect effects of pesticides on other non-target species -invertebrates, and aquatic fauna and flora, for example?

• The report focuses on effects on food chains and habitats; what about the effects of endocrine-disrupting pesticides?

• These effects all result from the legitimate use of pesticides: what new curbs on pesticides use will be effective?

The indirect effects of pesticides on birds. L.H. Campbell and A.S. Cooke (eds). Joint Nature Conservation Committee, Peterborough, 1997, 18pp.

[This article first appeared in Pesticides News No. 36, June 1997, page 3]