Blank Postcard of the Great Flight Cage at the Zoo, by Capitol Souvenir Company, 1948, Smithsonian Archives - History Div, Blank postcard of the Great Flight Cage at the National Zoological Park. Various birds are perched beside a waterfall and the pool below it. The message side is blank, but it has a printed note: "Great Flight Cage--A group of Great Birds in all their majestic and colorful splendor." The front has a white border..