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Volume 76: debated on Wednesday 3 April 1985

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asked the Secretary of State for the Environment what study he has made of the effect on swans of the use of lead shot by anglers.

There has been a number of scientific studies by the Nature Counservancy Concil and other organisations. Recent evidence shows that there has been a small increase in the overall swan population over the past five years, but it appears that in excess of 3,000 swans continue to die each year from lead poisoning caused by ingesting anglers' weights.

asked the Secretary of State for the Environment (1) if he can indicate from his Department's recent surveys what effect on the swan population has been registered by industrial pollution, diesel fumes and pollution of waters by increased river usage of diesel-driven vessels, dredging and the reduction of riverside vegetation as a result of pollution and dredging; and if he will make a statement;(2) what effects the increased use of herbicides and insecticides has had on the swan population;(3) to what extent, in determining lead poisoning in swans, a separate analysis was made of the effects of lead shot from gun sports; and if he will make a statement.

The 1981 report by the Nature Conservancy Council, "Lead Poisoning in Swans", examined all causes of swandeaths. Post mortem examinations in 1980–81 showed:

CausePercentage of deaths
Lead poisoning39·2
Collisions with overhead wires and by other structures27·4
Disease and infection10·4
Internal injuries10·0
Shot or deliberately killed5·5
In the period October 1981 to January 1985, 55 per cent. of post-mortem examinations indicated lead poisoning as the cause of death. Evidence from all postmortems in the period 1973 to 1981 showed that pellets of split-lead shot used in angling were present in 58 per cent. of swans examined, whereas gunshot was found in less than two per cent. of cases.

There is no evidence that industrial pollution, herbicides or insecticides have been a primary cause of death in swans.

In dealing with the suggestion that fumes emitted from petrol-engined boats may cause lead poisoning of swans the 1981 report states:

"Evidence from blood lead levels in swans shows that individual birds feeding on the same stretch of river may have very different blood lead levels. The considerable variation between individual birds can only be accounted for by differences in the amount of particulate lead ingested by each individual bird. Such variation is not consistent with the uptake of dissolved lead direct from water, and this must be discounted."

The 1981 report does, however, acknowledge that the problem of lead poisoning by anglers' weights seems to be particularly acute in waterways which do not have an abundance of aquatic vegetation, often as a consequence of an increase in river traffic. The report suggests that this may occur because discarded or spilt shot may remain more easily accessible to swans where vegetation is sparse.

asked the Secretary of State for the Environment if he will list the areas within the southern and eastern counties of England and the parts of northern England and Scotland where the swan population has increased over the last 10 years giving numbers and percentage figures where available; and if he will make a statement.

Information on increases in the swan population over the last 10 years is not available. However, the Wildfowl Trust conducted a national census in 1978 and again in 1983. In this five-year period the overall population increased by 7 per cent. The following counties in England and Scotland showed increases of over 10 per cent. in the period:

County (old boundaries)Number of SwansPercentage Increase
Yorkshire, West Riding19122719
Leicester and Rutland14426886
West Lothian8912
East Lothian8310729
In addition, the following counties showed increases over 10 per cent., but in these cases either the census coverage was poor or the figures are regarded as suspect from other knowledge, and the figures must be treated with caution: Durham (51 per cent.), Yorkshire, North Riding (230 per cent.), Shropshire (41 per cent.), Stafford (55 per cent.), Essex (53 per cent.), Somerset (27 per cent.), Cornwall (136 per cent.), Inverness (59 per cent.), Kincardine (200 per cent.), Stirling (183 per cent.), Kinross (100 per cent.), Lanark (209 per cent.), Dumfries (160 per cent.).