The finches land on the seed sock and each season need a little time to get used to it. They peck right through the cloth but as the dozens of eaters do their work, the level of the seed inside naturally drops. At first, some birds land at the top of the sock while the seed level has dropped below that point. They peck a few times and realize they aren't getting any food so they slide lower to where the seed is. After a couple of hours, they know to look at the seed level before landing.
The robins and junkos are used to finding seeds and such right on the ground and are not comfortable eating from a feeder. The crows and some jays and blackbirds are literally too big to fit on a feeder but carefully comb the ground under and around the feeder to find food that has been dropped or spilled from the feeders on the pole.
Most of the aggression I have seen appears to be within a species. Males will fly as though to land on top of a female and she will fly off, sometimes to another eating spot and sometimes not. From what I can tell, males will displace other males and females will displace other females but almost always within the same species. It does seem that smaller birds stay away from, and out of the way of, larger birds. Doves and crows are among the largest and when they land, the smaller birds often leave.
There is a large almost hemispherical baffle on the post holding the feeders and it generally seems to discourage squirrels from getting into the feeders. Two or three squirrels regularly comb the ground under the feeders very carefully as does a chipmunk or two. They have been doing so all winter. I guess rabbits and deer may also eat some of the grain but I haven't actually seen either at the feeders nor clear sets of tracks in snow.
We purposely put the feeder out in the middle of our back lawn where we can see everything there. We have had the feeder up for about two years and so far no hawks or cats or other predators have appeared.