secret area #1 via route 118. The birds nest.
a. requirements
#1. A LOT of ultra and great balls
#2. The h.M. Surf and waterfall
#3. Beat the elite four 
directions
 in the town with the flying type gym go down but stay close to the left side in a opening go there use surf, now there is another tiny island out here but skip that, ang go up. you will come to a waterfall skim it now you will find corpfish, polliwag and krabby up here, so keep going ad ytu wiil soon find a stair case or a opening in land. here is a little maze but it's easy. 

b. whats here
here are 3 doors each containing a legendary bird's (Zapdos,Articouno,and Moltres) there are  a infinite number of birds. Meaning that you catch till you faint. Zapdos the electric/ flying types it is on the right side you will need surf, Articouno is ice / flying type and in the middle, and moltre's the flying / fire type is on the right. NOTICE: to get to articuno's nest you will have to go through 2 ice puzzle's. moltres is a clean shot through and zapdos is surf & walk. 


next : the regi's- regirock - regiice - and registeel. a 3 part guide

tyzhon : Good job! Just try to type some more and go more in depth.

Thank you for your effort!

mohammedroxx3 : thanks man. i'll send you a sneak peak of the regi- guide part 1/3 for replying being the first to my guide