Chemicals known to affect brains of common garden birds, and to kill unborn chicks, found in most feather samples

Conservationists have called for restrictions on pet flea treatments after research found songbird feathers widely contaminated with substances that can damage the birds’ brains and kill unborn chicks.

Almost every feather sample tested from five common species of UK garden birds contained either permethrin, imidacloprid or fipronil – all insecticides that are banned for agricultural use but still common in pet tick and flea treatments.