Okay, I had to do a lot of driving today, and as I was driving along the interstate I pondered the puzzle of the pigeons. (Ooh, alliteration!) It just didn't seem to make sense how a homing pigeon would just hang around on Maddy's doorstep. A homing pigeon should fly home when it was released, and one would think that Maddy would notice if the pigeon was actually living on her doorstep. Then, I considered another possibility: IT'S NOT A #@*%ING HOMING PIGEON!
We all seem to have assumed that the bird was a homing pigeon, because homing pigeons are what a person would normally tie a note to. But using pigeons never seemed like a normal or effective way of transporting messages. I started out favoring the theory that Mr. Zipp was dropping homing pigeons on Maddy's doorstep, since there didn't seem to be a way to make the pigeon consider Maddy's doorstep to be "home" without her noticing. Also, since the third note was just tied to the doorknob, we already knew he or an accomplice was close.
Then I realized that the bird just stands around with a message tied to its leg, and when someone releases it, the bird flies off. This does not require any particular talents other than being somewhat tame and lazy. It's possible that it even was given a tranquilizer to make it easier to transport and make sure it didn't fly away. So this would mean:
1) The bird must have been physically left at the door, which narrows down possible suspects for who Mr. Zipp is. (Although the third note and the whole "you will know the password" thing already indicated that he was close, the timing may eliminate more suspects. Who actually had a opportunity to drop the bird?)
2) The purpose of the bird was (at least in part) misdirection. It was a way to make a message
look like it came from somewhere else. Perhaps to protect the identity of Mr. Zipp?
3) This provides a possible explanation for why Mr. Zipp didn't use another pigeon after Maddy sent a reply. If it's not actually a homing pigeon and is just randomly flying around, Mr. Zipp may have been worried about Maddy seeing the pigeon again before he did. If Maddy's neighborhood became filled with pigeons that still had Maddy's replies tied to their legs, she might get suspicious.
4) If the above is true, then it is likely that Mr. Zipp did not in fact get Maddy's message from the pigeon. So how did he know she sent the message? His next message only came after Maddy's reply after all, and we are assuming is a reply to that. (Although I just established that assumptions are dangerous, and we still haven't figured the third note out yet.) Maybe he's watching Maddy's videos, or maybe he saw the message before it was sent...
So, does my logic seem sound? Does anybody have more ideas? I'm going to go back to watch the videos again. Maybe I can deduce something from the windows of opportunity for leaving the birds.