Near the ending of Close Encounters of the Third Kind, Roy and Jillian are frantically trying to reach Devils Tower in Wyoming.
The U.S. Army has issued road blocks and they have made false claims about toxic nerve gas in the air to prevent the public from being in the vicinity.
Roy purchases a gas mask and a cage containing two live birds. They both put on gas masks. As they drive closer to their destination, they encounter several dead animals on the side of the road. Jillian checks the two birds and they are still alive. They both realize that it's a hoax and remove their masks.
They are stopped by uniformed workers with gas masks who take them into custody. When they are stopped, the birds are still alive. When we see Roy and Jillian being taken away, we see one of the uniformed workers carrying the cage and both birds appear to be dead moments after Roy and Jillian are removed from the car.
How did the two birds die? The movie makes it clear that the Army created this hoax and that the air was fine. Did the uniformed officers do something to the birds to convince Roy and Jillian that the air was toxic?