People who frequently see birds visiting their gardens are being asked to be vigilant by an expert. He said garden feeders, frequently used much more during the colder months, can rapidly become a concealed danger if food gets wet or starts to go off. Richard Green, a bird feeding expert from bird food supplier Kennedy Wild Bird Food and Pet Supplies , is warning households to inspect their bird food for danger signs and how to protect food from the rain. He explained: "Once damp, within 24 to