Don't look at how many birds I have remaining. I killed my first bird out of order, which is why it says 198 birds left after my first kill. If you simply follow all 4 videos and use the map with the number I placed on the video for each kill, you will find all 200
This video contains the locations of pigeons 101 through 150 as detailed on the map above.
Killing all the flying rats will get you the Endangered Species achievement