According to tradition, they founded Tenochtitlan ( "Place of the High Priest Tenoch" ) after much wandering when they saw on an island in Lake Texcoco the sign that their god Huitzilopochtli had indicated -- an eagle perched on a cactus, eating a serpent .
The eagle was eating a rattlesnake.
It doesn't say what type of serpent the eagle was eating therefore it's unknown. Teh system knows it ate a serpent so when I said rattlesnake it said no.
( z1 eat :ARG0 ( z2 eagle ) :ARG1 ( z3 rattlesnake ) )