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Lead shot shown to be major cause of bird deaths

A new scientific study shows lead shot has severe toxic effects on the immune system of wild birds and is a prime factor in their demise

wild ducks in flight

Spent lead shot significantly weakens the immune systems of wild birds and is a major cause of death, according to a newly released scientific paper.

The paper entitled Immunotoxic effects of lead on birds was published in Science of the Total Environment. The harmful effect of spent lead shot on birds has been known for some time and has led to bans on its use over wetlands in Scotland and for duck and goose shooting in England. Several European countries have also introduced restrictions on its use.

Birds are known to accidentally swallow lead shot as part of their feeding behaviour, mistaking it for grit that they swallow to aid digestion.

Previous studies have found that lead poisoning can be a serious problem for wild birds, especially waterfowl. Additionally any scavengers that eat the bodies of poisoned birds are likely 
to be poisoned themselves.

lead shot

Calls from shooting community

The new study is likely to boost calls by those in the shooting community calling for further restrictions on lead shot and greater use of steel and bismuth.

Lead poisons wild birds

Lead, like other heavy metals, is very difficult for the body to get rid of and tends to accumulate in the liver and kidneys. Previous scientific studies have suggested that lead poisoning may result 
in the deaths of three million 
birds a year in the US.

The new study pulls together evidence from several others that have looked at the effect of lead 
on the immune systems of birds. The researchers found that even low levels of lead in the blood of birds can significantly interfere with the balance of different elements in their immune systems. An alteration of this balance makes the birds more vulnerable to disease.

In adult birds the level of lead exposure needed was quite high and would produce other symptoms. But in young birds even a very low level of lead in their blood had a significant effect on how well they were able to fight off disease. It was so significant that the researchers concluded that “lead poisoning is among the main causes of wild bird mortality”.