We've been feeding birds since we moved here in 1986. Black oil sunflowers is mostly what we feed and we get the seeds that are still in the hulls. My birds never seemed to go for the de-hulled ones. I've always just used a cedar hopper style feeder on a conduit post with a squirrel baffle. Someone said above that squirrels can't climb 1" conduit...bullcrap. My squirrels (and coons) easily climb conduit and would empty 20 pounds of seed in a day without the baffle. And it's not that they just eat the seed, they hoard it. They'll carry it away and store it. And as long as the squirrels are in the feeders, no birds get to eat. The baffle also stops coons, too. I imagine mice would climb the post too without a baffle. If you're gonna feed, then make sure the feeder is only for the birds. You can feed the other critters with other means. GET A BAFFLE or make the feeder critter proof by other tactics.
My buddy has bear issues with his bird feeders so he hangs the feeder 14 feet with a cable that goes up to hang from a pulley on a branch. Last year, he needed to re-hang it and was 20+ high on the ladder and it kicked out and he came crashing down...He broke his leg horribly. Almost a compound fracture. It caused him to miss a 2 week ocean fishing trip. It may have been a blessing in disguise because, throughout all the scans, the doctors also found pancreas issues before it turned cancerous. He then missed almost all of hunting season. He went out for just a few hours at the end of 2017 just so he could keep his 50 year bow hunting streak in tact.
We also feed suet. It needs to be protected as well. Pretty much everything will eat suet. I make suet from lard, peanut butter, cornmeal, oats, flour and sugar. My suet doesn't get nasty in the summer. I have fed it in summer but I don't normally feed it in summer. There's enough insect protein out there that I'd rater the birds eat instead of my suet. The birds prefer the homemade suet over store bought suet. I could never get them to eat straight lard or fat trimmings. One issue I have with suet is starlings. Starlings never eat the sunflower seeds but a flock of stinking starlings will set upon the suet and devour it. I despise starlings and I shoot as many as I can. I shoot them with .22 cal Super Colibri made by Aquila. They are a pretty cool ammo that not many people know about. They are low power .22 cartridges that are powered only by the primer...there's no powder in it. It's not much louder than a dry fire so other critters or neighbors don't realize you're shooting.
We feed hummingbirds too. 4 cups of water and 1 cup of sugar. No need to boil the water and don't add food coloring. As mentioned above, a bully will take over and guard the feeder. Several feeders spread out so they can't all be seen by the bully at one time helps to stop feeder hogging. Feeders with bee-guards are almost a must. And spraying the post with permethrin or other ant deterrent keeps crawling bugs to a minimum.