The robins often exhibit active 'anting' behaviour, in which they pick up one or more ants in their beaks and rub the insects over their feathers. Many species of birds also do this. It was thought that formic acid squirted by the distressed ants cleaned up feather-munching lice and mites and got rid of bacteria and fungi. But, it turns out, the volume and concentration of formic acid isn't sufficient to do the job. Instead, it is likely that birds like the grey-headed robin are actually disarming the ants prior to feeding on them. A beakful of formic acid is just too pungent but half a beakful is piquant.
