Poor plucked guy. We have a clear opinion here: this rooster isn't lonely by choice, he's a refugee, and you, brave reader, are his safe harbor. The real question isn't whether you *need* hens, but whether you want to turn your yard into a full-time fowl sanctuary. Watching him get chased and de-feathered is the kind of 500 clucking days of feathered art and fowl play that nobody signs up for, yet here you are, feeding him duck food and wondering if a solo rooster can be happy.
The short answer is: he's probably fine with the visiting hens and geese, but fine isn't the same as thriving. Roosters are flock animals, and while he's choosing to stay in your yard, that choice might be more about survival than contentment. He knows the neighbor's flock has a bully, so he's parked himself in the one spot where he won't get pecked again. The hens that graze through are social enough to keep him from going stir-crazy, but they leave. That's a lot of alone time for a guy who used to have a crew. You don't need to rush out and buy a dozen layers, but if you're feeling generous, one or two friendly hens could turn his yard time into a real party. Think of it as Pumpkin's ghostly costume is egg-citingly spooky and cluck-tastic fun, except the costume is his dignity, and the fun is him finally relaxing.
Now, about the diet. Sunflower seeds are a treat, and duck food is better than nothing, but it's not a long-term plan. Roosters need a balanced feed with enough protein to grow those tail feathers back. If you're going to keep him around, grab a bag of layer crumble or flock raiser from the feed store. It's not complicated, and it'll do more for his morale than any amount of seeds. Also, give him a place to hide. A simple dog house or a pile of brush will make him feel like he owns the place, not just squats there.
The bigger picture here is that this rooster has chosen you, and that's both an honor and a responsibility. He's not asking for much, just a little security and a snack. But the open question, the one we'll be watching, is whether the neighbor's bully makes another move. If that rooster shows up in your yard again, you might have a full-blown fowl feud on your hands. And we all know how Our coop is closed for app-vertising: no more fowl sales pitches ends when chickens get territorial. Keep an eye on that fence line.