Or maybe they have been captured and kept under lock and key. Birds should be free to fly not caged up in an unknown location where the sun can't reach them. People should be free to experience the beauty of these wonderful creatures. Although there are some, who have attained information of the presence of them have potential to cause harm. The authorities have noticed these threats and as a consequence, in an attempts to protect them, have taken action in the form of capturing these birds and keeping them in captivity away from prying eyes.
Now access to the birds involves a long screening and verification from the people in power, the ones in charge. No free admission. No public access.