There are many different reasons why you might want to photograph a group of birds. Sometimes you just can’t get close enough to make a compelling photo of a single bird, but you can get something good by featuring multiple birds in the same photo. Four Short-billed Dowitchers make for a nice photo even at a distance where a single one would be a bit skimpy.
Even just adding a second bird lets you zoom out a bit on a composition that would otherwise have too much empty space, as you can see with the pair of American Coots, a species that is often difficult to approach.
When you are photographing a group or pair—because you’re too far away or for any reason—you do want to figure out which individual bird is the focal point of the photo. In most cases, only one bird is going to be fully in focus, and usually it’s the closest one to you. There are exceptions. Sometimes the biggest or most interesting bird is in the background and should be the focal point, and sometimes you can get a good focus on multiple birds. If the birds are moving, the “star” of the shot may be changing quickly.