I am beginner in all of this and also I would like to know why this is happening. In this example every generation have 20 new genomes (birds), 3 best stay from

I am beginner in all of this and also I would like to know why this is happening. In this example every generation have 20 new genomes (birds), 3 best stay from previous generation (elitism), rest are effect of mutation. Maybe mutation rate/range have to be tweaked. Current solution is best what I found so far.