When the military tried to use chickens as an advanced warning system against biological or chemical attack, almost all of the animals died within a week and a half. Not to be deterred, the Marines decided to try again only this time using pigeons.
The Marines were doing everything they could to keep the pigeons fro meeting the same fate, including giving them bottled water and finding people with experience caring for pigeons to take care of the birds.
But even if chemical or biological weapons are used in Iraq (which, obviously, looks like it’s not going to happen at the moment), pigeons likely have the same flaw as chickens — biological and chemical weapon are going to affect the birds differently than human beings.
Source:
Marine pigeon force may detect attack. Ravi Nessman, Associated Press, March 16, 2003.