Slightly OT: If you ever happen to be in Oklahoma City, the American Pigeon Museum[0] is a nice diversion - larger than you'd think, and lots of interesting tidbits to be had, including history on the passenger pigeon. I saw it in passing on an unrelated trip, but it turned into the best story to tell from OKC.<p>[0] <a href="http://www.theamericanpigeonmuseum.org/" rel="nofollow">http://www.theamericanpigeonmuseum.org/</a>
The Passenger Pigeon lived in an environment where flocks were found everywhere. An individual pigeon could safely "wander off" and find a new flock. Once the population level descended below a critical level, the species was doomed. In order to bring them back, you would need to breed them by the millions before releasing them.<p>A more practical worry is the Rusty Blackbird, which has declined fast in recent decades and may be headed the way of the Passenger Pigeon.
There is an RFC for IP via carrier pigeon [0]<p>[0] <a href="http://tools.ietf.org/html/rfc1149" rel="nofollow">http://tools.ietf.org/html/rfc1149</a>
If I had to, I would stake money on a Woolly Mammoth* being brought back in my lifetime. I'm 43.<p>* This includes an elephant/mammoth hybrid/chimera.