Screaming is a difficult one. A lot depends on why your bird screams. Is it loneliness? Sexual frustration? Illness? Attention seeking? Or just plain boredom? Sometimes, a bird can begin screaming for a reason and when that reason is repaired, he continues screaming because he has grown to like it. It can be really, really hard to get them to stop.
First of all, watch birdie closely and see if you can figure out if there's a trigger (handy that you're at home most of the time). Some birds call at the same times every day. My female Alex calls at 7.30am *sharp* and again at 4.30/5.30pm (depending on daylight saving). She calls for about twenty-five minutes and graduall stops. I assume this is 'flock calling' or the usual bonding call that flock members send out to call in all the stragglers before roosting. The odd thing is that Madge does it religiously while Barney doesn't bother. ????
My Corella also flock calls, but only briefly and half-heartedly in the mornings. The thing about her is that she's EXCEEDINGLY LOUD and I die a million deaths thinking of the neighbours. No one's complained so far, but then they could be sitting in their houses wishing me and my birds in perdition!
So! I've figured out a way to defuse 'Setta's bellowing in the late arvo. Normally, I would give all the birds their daily veggies and pellets in the mornings. I no longer do this. I give the pellets and clean water in the mornings, but save the veggies and fruits or whatever until four thirty. I give half of it and then wait. When the girls start yelling, I give the second half and that seems to keep their fat little beaks busy until it's nearly sunset. They might send out a few well-chosen shrieks, but mostly they settle down and nod off once the sun's set.
I wonder whether your bird responds to wild birds? Rosetta does, calling greetings to the wild corellas when they fly over. The Beaks *used* to respond to the (very large, very vocal) flocks of Rainbow Lorikeets that visit our trees every day. Since I've been giving them the late feed of veggies, though, they no longer bother. The thing is, R'Lorikeets are *notorious* flock-callers and bellow until every bird within a ninety-mile radius has come to roost (exaggerating here, but you get my drift?). I've heard of local birds that respond to the RLs like clockwork and perhaps that could be affecting yours? If he's hearing roosting lorikeets, he might be responding.
Watch him for a few days and try my veggie idea (can't hurt?). Let us know how you get on. I'm sure others will chime in, probably with more useful tips than mine.
Betrisher
PS. Covering his cage isn't entirely the best way to shut him up. It's more likely to make him resentful.
PPS. Other idea! Does he talk? You could try asking him to say things during the loud period and reward him heavily for obeying. I had some small success with Madge doing that at our old house. I'd ask her to say 'Hello' and when she did, I'd reward her. It became tiresome, though, as it meant I had to sit with her saying 'Hello' for the half-hour when she would normally yell. -_-