Green tree pythons are very finniky eaters. I wouldn't feed that one anything except what he is feeding it, or else it may not go back to what he was feeding. No pythons will eat fish (to my knowledge), and I just wouldn't feed birds because it will be hard to get them feeding on mice/rats again.
Give a GTP a quail and then a mouse, it's like going from a UDSA Grade A Ribeye to chopped steak.
I don't really think it's even possible for there to be a boa/python intergrade - the species are too different. Maybe i'm wrong? It would be interesting to see...
I'd keep them on what they're eating. You won't want to give him that GTP back!
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0.1 Licorice Stick Black Rat
1.0 Black Rat
0.1 Vietnamese Blue Beauty
1.0 Green Tree Python
0.1 Texas Bairds Rat
The educated are the few. The uneducated are the masses.