1. The objective size determines the brightness and level of details of image. It has nothing to do with FOV.
2. FOV is determined by eyepiece design. You can have wide FOV 8x32(e.g. Nikon EII) or narrow FOV 7x50 (e.g. Fujinon FMTSX)
3. For bird watching, FOV, weight, waterproof, close focusing distance and focuser speed are more important. Think about how you will use the binos. For star watching, objective size, coating quality, magnification are more important.
Just my two cents.
