IT LOOKS like tits are becoming latter-day canaries. While the songbirds famously gave coal miners warning of toxic gases, the blue tit and the great tit鈥攖wo of Europe鈥檚 most attractive garden birds鈥攃ould help keep tabs on pollution.
Tom Dauwe at the University of Antwerp in Belgium found that levels of heavy metals in the tail feathers of great tits and blue tits give a good picture of levels of pollution around where they live. Dauwe and his colleagues analysed adult tail feathers from 32 great tits and 8 blue tits caught in an area contaminated with lead, cadmium, copper and zinc from a nearby metal works.
Their feathers had picked up much higher concentrations of these metals than feathers from 50 great tits and 10 blue tits collected at a 鈥渃lean鈥� reference site on the university campus. Lead concentrations were 34 times higher, for example, in feathers from great tits caught at the polluted site.
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鈥淢etal concentrations in feathers can be higher, and hence easier to detect and quantify, than the metals in blood or tissue samples,鈥� Dauwe says. He adds that the birds are easy to catch in nesting boxes when they are feeding their young or while they are roosting during winter. 鈥淭he feathers come out easily and the birds are not stressed by it.鈥�
Dauwe says that the procedure is far less traumatic than the alternative鈥攖aking a blood sample. And the feathers grow back in as little as a month
In a paper that is scheduled to appear in a forthcoming issue of the journal Ecological Indicators, Dauwe points out that tits seldom stray far from home, so they produce a reliable measure of pollution levels for a small area. Although feathers have been used before to measure pollution, they have mostly been from birds of prey that roam over large areas.
By studying birds that had died naturally, the Antwerp team confirmed the correlation between the amount of metal found in the feathers and that in liver, kidney and muscle tissues.