Varanus - it is quite common for a goshawk to refuse rabbits at first. My female NA is now five and is deadly on jacks and cottontails, but her first years she would not chase either until November. I think it had more to do with maturity than weight or a drop in temperature. I would just focus on birds, carhawk if you need to, then try rabbits a couple of months down the road. Best of luck ...
I have had several savannah monitors and I really liked them. I've gotten out of it for a while while my kids are little but I plan on getting back into it later on. I'd like to have a couple of niles and maybe a water some day.
I take it that from your user name you love monitors? I had an article in January's Reptiles magazine and a picture in the July issue under the breeders choice. I use to breed various monitors but mostly breed snakes now...
Just thought I'd say hey, since it appears you're a fellow herper!