Chickens are working with the US Army in order to detect a possible Iraqi chemical attack.  They are trusted sources of information because they are alive; and the soldiers will trust a living thing's reaction to gas before a sophisticated chemical detection system.

Apparently some of those chickens had to take a sick leave and have been replaced by pigeons.

http://story.news.yahoo.com/news?tmpl=story&u=/ap/20030402/ap_wo_en_ge/na_gen_us_iraq_critters_1