IN the mines of East Lancashire canaries were used to detect poisonous gases. These birds were therefore pollution indicators.

Researchers in Belgium have found that blue tits and great tits could be about to help us measure pollution levels with the minimum of fuss. They have found high levels of heavy metals in the tail feathers of these birds. They found lead, cadmium, copper and zinc in an area close to a nearby metal works.

The scientists compared the levels from feathers gathered from a cleaner site. The feature collection obviously caused less stress to the birds than the more traditional methods of taking blood and tissue samples. They catch the adult birds at nesting sites and the feathers grow back in less than one month.

The tit family seldom stray far from home and this can be correlated to specific areas. Feathers have been used before as pollution indicators but work has only so far been done on birds of prey which roam over large areas.

By studying birds which had died naturally the Belgians confirmed the correlation between the levels of metals found in the feathers and that of the liver, kidney and muscle tissues.