Well, i guess it depends if we are talking about a magnetic pole shift or a cataclysmic pole shift. A magnetic pole shift is said to occur about every 300,000 years, and considering the last one to occur was 780,000 years ago, its safe to say we are overdue, but have been for some time. At most they theroize that it may affect some migratory animals but that would probably be the extent of it. From what ive read they take upwards of 5,000 years to complete once it starts, though again its all theory since obviously no one was around to see over 3/4 of a million years ago. Part of what i read i included a link to in case you want to check it out. what i found to be neat is the possibility of temporarily having 3 or 4 magnetic north and 3 or 4 magnetic south poles at the same time

could you imagine the headache that would cause? lol
Now, that being said, a cataclysmic polar shift on the other hand would seriously screw us all up, thats where the poles dont reverse magnetically but where they physically move x amount of miles permanatly, not just temporary like with the magnetic reversal, but that requires an outside source to knock the earth out of whack, it would be interesting to live thru though.. watch the sun race across the sky and have your 96 degree day become twilight and snow start falling ( kinda like it is outside atm, i had hoped we were thru with the snow lol) . Ahh this topic lead me into alot of very interesting reading. Part of what i found out is that the mass animal deaths are becoming more and more frequent at an alarming rate, some are saying its the methane gas released from fault lines that kill off the birds but it sounds a lil too conveinant for me to believe.
http://www.dailycommonsense.com/what-is ... ift-thing/and for the catclysmic part...
http://en.wikipedia.org/wiki/Pole_shift_theory