Borax for curing a rabbit pelt is NOT the way to go- as you will need to scrape it-- and the skin is so thin, you could potentially ruin/tear the pelt up. Using the Alum/salt method means one does not have to remove the stuff that sticks to the hide before it is cured, then the cured hide is stronger and can survive the cleaning up process. Also, when using Borax, you have to have the hide stretched out flat, and in a very warm, dry, bright place to prevent molds and fungus from growing...
However, Borax is the BEST way to cure a bird's 'hide' Birds skin out a lot cleaner than mammals do...