When selecting binoculars for birding several things need to be kept in mind. Binoculars are not all created equal. Particular features are needed to maximize the experience of the view. All binoculars can focus at infinity, but their close focus specification will vary. Be sure the binoculars that you select have a close focus specification of 10 feet or less. When you are on a birding trip it is very likely that a bird that you are watching may flitter and land on a branch that is closer to you!
Magnification selection is a personal decision but a 7x to 10x is recommended. Keep in mind that larger magnification means that the field of view will be smaller.
Generally speaking objective size will determine how bright the view is. The larger the brighter. The larger the heavier also.