It's somewhat similar to trying to hit a bird with a shotgun (wide field binoculars) versus a rifle. The greater "spread" that a wide field of view gives you helps in initial target acquisition and helps you stay with fast flying birds. This isn't an issue if you know exactly where the birds are ie. on a bird feeder or similar but would be for something like a prairie falcon zooming over your badlands at 60 mph (and many other birding situations). The extra wide field 7x35s are probably not absolutely necessary, although very nice to have, especially if you don't use binoculars with glasses/spectacles. I'd require at least the industry standard though, which seems to be about 110m at 1000m for 10x, 130m at 1000m for 8x and 140m (I think) at 1000m for 7x.
Regarding filling the view with the bird - it's very seldom possible to do that with binoculars unless you're observing city birds and/or very large birds. Even with a spotting scope it's not easy sometimes.
Regarding filling the view with the bird - it's very seldom possible to do that with binoculars unless you're observing city birds and/or very large birds. Even with a spotting scope it's not easy sometimes.
