What is Nietzsche refering to when mentioning the birds of prey and the lambs?

Check out the link below;

http://fitzenctrans.blogspot.com/2013/01/nietzsche-and-nature-imagery-explaining.html

To be viewed as a motif to Nietzshe's Master Morality - Slave Morality dichotemy (Noble-morality(Nietzsche's proposed prescription) being a decendant of the former)) it is meant to illustrate differences in will to power between prey and predator as built into nature.

Put another way, (and most definitely not to be conflated with Nazisim), it is a naturalistic account of how men of either catagory simply accept their will to power ( through calculation, responsiblity) or deny their will to power, turning it in on themsevles, and thus resenting anybody exceptional.