Actually DARPA has funded a number of small UAVs with bird like properties. The Aerovironment humming bird [1] is one such example.
If you want to see some some overhype check out the video in [2]. Basically it has a the humming bird types everywhere. I suggested to a friend who shared that video with me that perhaps the military would add 'skeet shooting' to their rifeman training so that some members of your squad are designated MAV suppression :-)
Its wonderful robotics, I'm not sure its so great for folks who care about the civil liberty aspects, or the folks who have to worry about a larger threat surface.
Even if it can't carry cargo one day, it could still be outfitted with a tiny camera, some sort of radio, and maybe a little onboard storage. Paint it like a bird, and boom — a sneaky surveillance system.
Do you think DoD did not think about it previously while they put transmitters on birds? I think it has to do with autonomy, speed (a real bird is more energy efficient, is more powerful and has a longer flight autonomy), and electronic signals betraying you (you have to physically come back with the data, not upload/transmit).
It's one thing to carry out experiments that might one day be used on a battlefield. Such pie in the sky thinking is pretty constant.
It's completely another to adapt a working prototype into a viable device, and as far as I know nothing to date has come as close as that video I just witnessed.
In addition, secure two-way data feeds in real time is pretty much a solved problem, and is currently being used on pretty much every UAV in existence today.
Talk about hiding in plain sight.