... on comparative aspects of anatomy and physiology. But how do all of us sense and respond to an infection? We cannot see, hear, feel, smell or taste bacterial and viral pathogens, but humans and animals alike are fully aware of symptoms of sickness that are caused by these microbes. Pain, fatigue, altered sleep...

... their time at rest ( Fig. 3 ). Such responses are considered to be stereotypical sickness behaviours ( Hart, 1988 ), and have been reported previously in birds treated with LPS (e.g. Bonneaud et al., 2003 ; Owen-Ashley et al., 2006 ). Evidence for a trade-off between thermoregulation and sickness behaviour...