I managed to debug the BP and the StoreTargetsWithinThisRange variable was to low for my world. Is it any reason to this variable?
Yes there is an important reason for that variable. The Birds will only store targets within that range of their starting position. This is how say the Seagulls stay near the shore and the Pigeons will stay in town center. This was done so that the Birds will stay in the area that you place them in. You can set the variable to a huge number if you want all the Birds to all fly everywhere.