A study with great birds shows that exposure to heavy metals such as cadmium and lead depletes their vitality and makes them more aggressive birds.
The great tit, (Parus major), is a small insectivorous bird with yellow plumage that inhabits all of Spain and much of Europe. The abundance of this species and its defined behavioral traits made it an ideal study subject for researchers at the University of Antwerp, in Belgium, who were trying to find out if the intake of heavy metals affected the personality of birds in any way, just as it happens with human beings. It is already known that exposure to these toxic substances produces in people from irritability and extreme fatigue to depression.
Belgian scientists were dedicated to monitoring the habits of the common coal that lived in the vicinity of the Umicore refinery where they work in the smelting of metals with abundant emissions of lead and cadmium, among other pollutants. The experiment consisted of capturing 250 specimens from different locations - closer and farther from the manufacturing facilities - and examining how they behaved in the laboratory. They found that chickadees with greater contact with heavy metals, as they were able to verify by analyzing the chemical composition of their eggs and feathers, were more inactive. The lead and cadmium had "quenched" his natural propensity to be curious, to explore the environment.
Get out of my nest!
In addition to the decrease in their activity observed in the laboratory, in a second stage of the study, they marked the captured specimens and returned them to their original environment, where they again observed their habits and reactions not only to natural stimuli, but also to others induced by scientists, such as the introduction of a stuffed bird in their nests or the reproduction of recorded songs to induce them to believe that a competitor was haunting them.
From the study, they ensure that the males were much more aggressive against the decoys imposed by the researchers. Furthermore, their aggressiveness increased as they approached the factory area. While the females showed a much more protective behavior than usual with their eggs.
In short: lead and cadmium were making coal miners both more run down and irritable. The seriousness of this situation is that these characteristics make them more vulnerable to their predators.
On a plastic diet
Unfortunately, metals are not the only food threat to birds. Other recent reports indicate, for example, that more than 80% of marine species have introduced plastic - bags, bottle caps, etc. - into their usual diet, and that the percentage will skyrocket to 99% by 2050. It seems be, according to a study published in 2016, that they mistake it for food due to the smell: when decomposing waste in the sea, microbes generate a fragrant substance called dimethyl sulfide. And when ingesting the plastic, the birds can suffer intestinal obstruction, poisoning or malnutrition.
Image credit: a great tit and a blue tit in dispute./iStock.
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