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Toxic Metals Change Birds’ Personalities

Scientists have reported that toxic metal poisoning is changing birds' personalities. A recent study of Great tits has shown that they can become less curious and unwilling to explore new places when exposed to high levels of heavy metals.

Waste in the Environment

Heavy metal waste in the environment such as cadmium, zinc and lead can be seriously harmful to birds. The Great tits which live in high-pollution areas are becoming more nervous. This tendency leaves them more vulnerable to predation as they are too lethargic.

The Impact of Human Activity

Metals are naturally found in the environment, but their levels have become much higher due to human activity. Nothing new there! Researchers from the University of Antwerp, Belgium, have now looked at Great tit behaviour and how it relates to their proximity to industrial sites. Five populations of the birds were studied which lived at various distances from a smelter which was polluting the environment.

Changing Minds

The scientists believe that the metals change the chemistry of the birds’ brains although there is no proof of this as yet. But if metal exposure causes lethargy, it makes sense that the birds which are exposed to the highest metal burden will become the easiest prey. The predators will also be impacted as they absorb more heavy metal themselves and so the effect of the metals spreads through the food chain.

The Symptoms of Avian Metal Poisoning

Birds are easily poisoned by heavy metals which impact the various species in different ways. The most common symptoms are constant thirst, listlessness, general weakness, depression, tremors, seizures and poor coordination.

250 Great Tits Examined

During the recent study more than 250 birds were caught and examined. The birds were taken to a laboratory where there was an area set up for them with artificial trees. The scientists assessed the behaviour and activity levels of the birds and found that the closer to the smelter they had lived, the less active they were.

The researchers also found that at polluted sites, birds’ eggs showed elevated levels of heavy metals as did the feathers of young birds. The specimens that they studied were ringed and then released back into the wild so the team could continue to study their behaviour. Once the birds had been reintroduced to their homes, the researchers began looking at the impact of heavy metal poisoning on avian aggression and nest defence.

Stuffed birds were placed in nearby nests, accompanied by a recording of male birdsong, to give the impression that an intruder and competitor was close by. The Great tits became aggressive towards the perceived threat and females became defensive of their nests. These behaviours did not change in line with the birds’ distance from the smelter. The researchers concluded that whilst heavy metals impacted birds’ willingness to explore, it did not affect their other personality traits.

Lead poisoning in humans may have declined as awareness of the dangers improved but birds continue to be affected by high levels of heavy metals in the environment.


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