The Griffon vulture is not a migratory bird, but it isn't uncommon for them to make their way into northern Africa, according to Hatzofe, who says the vulture's wing tag included a message asking anyone who found the bird to contact him or the university.

"My email address is on the vulture," he told CNN, "but I never got a message."

The Israeli government declined to comment on this story, and repeated calls to Sudanese officials went unanswered.

Hatzofe says that the real danger of claiming that GPS-tagged birds are spies is that it could prompt government officials to kill animals they capture.

"There is nothing new about birds tagged for studies, and if governments will not reject these types of rumors, then others will grab their weapons and hunt down wildlife -- the exact opposite of what conservationists want."