I can only speak for my own area (Lower Hunter, NSW), but since 80% of our population lives nearer the coast, few people ever see wild budgies all that often because they (the budgies) live in the drier inland part of the country. I s'pose people who farm on the western slopes and plains of NSW would see them from time to time, but I imagine most aviary escapees also live in the coastal fringe, so their opportunity to mix with the wild flocks would be limited.
Add to that a healthy and varied population of raptors (including about thirteen species of swift-flying falcons) and a massive, *massive* feral cat and fox problem, escaped birds don't stand much of a chance, especially oddly-coloured ones that aren't evolved to blend in with our native landscape. I've never heard of an escaped budgie being found again or of escaped budgies being seen in wild flocks. Maybe another member has and will chime in?
I don't know about New Zealand. Budgies aren't native there, so any 'wild' populations would have to be feral to begin with.
I'm well aware of how lucky I am to be able to look into the sky on any fair day and see at least three or four varieties of parrots! We get noisy flocks of Rainbow and Scaly-breasted Lorikeets in the gum trees in our yard. They come to eat the blossoms and their noise is deafening at times. It's also a bit disconcerting to be hanging out washing, say, and have a lorikeet zoom past, almost literally under your nose! Very occasionally, the high-flying species like Musk Lorikeets or Littel Lorikeets will visit, but you have to be lucky and sharp-eyed to see them. Mostly, I know they're there because of the calls.
In drier summers, flocks of SC2s and mixed flocks of Corellas (Little and Long-billed) visit the coastal areas looking for food and water. There are few sights to beat that of a large flock of big white birds wheeling against an intense blue sky! The sharp whiteness of their plumage and the faint flush of lemon-yellow on their undersides makes such a gorgeous spectacle: it's breath-taking. When I was young, we used to see flocks of thirty or so Galahs feeding on the roadside verges, but today you only see them in pairs or fours at the most. I'm worried about this! I'm particularly fond of the Galahs and wonder why their numbers seem to be declining in urban areas. When hubby and I were on our honeymoon, we rounded a bend on a hillside and had to stop because a flock of about five hundred Galahs was feeding on spilled wheat on the road. We waited for over an hour, watching them and enjoying the spectacular sight. All that pink! It was amazing!
A few years ago, an unusually big flock of Corellas hung around our area for a good six months or more. They're absolutely hilarious when they pause to rest and socialise (usually on power lines and tv antennas). They chat in small groups, just like a gaggle of housewives and generally swing and trapeze themselves acrobatically all the while. It helps that their voices are pitched pretty much at the same level as an older woman's. Many times, I've walked beneath a group of them, thinking it was ladies conversing in the next street! LOL!
Our house had a flat tin roof and in drought years we would always put out bread scraps and a seed/pellet mixture for the wild cockies. I had photos of over a hundred SC2s feeding on our roof, but sadly lost them when we moved. I'd had a sheet of clear plastic inserted in the iron roof and it was fun to watch the birds from beneath as they fed. They didn't seem to be aware of us watching and just carried on as usual, gobbling up food and squabbling amongst themselves. What a privilege that was!
More recently, we've had a small flock of Yellow-tailed Black Cockatoos visiting our new house. These birds are rather longer than the SC2s but are much more slender and graceful. They have an unusually slow and leisurely flight pattern and their call is far-carrying and plaintive: you always hear them a long time before they come into view. Last year, we had a pair feeding its young in our big gum tree and that was really special! Then, not long before Christmas, we had thirty-six adult birds visit our yard. Most stayed up in the height of the gum trees, but quite a few came down to feed on (of all things) our neighbour's crepe myrtle flowers! The black cockies generally confine themselves to forested areas and last year was the first in which I've ever experienced them on the urban fringe. I don't know what lured them down from the hills, but I'm certainly happy to see them!
Other lovely locals that I see less often are King Parrots, Eastern Rosellas, Crimson Rosellas, Gang Gang Cockatoos and, very occasionally, Glossy Black Cockatoos.
There are a few local parks where old-growth trees contain excellently suitable nest-holes. It's possible to walk around and listen in as the SC2s, Rosellas and Corellas raise their babies. LOL! The sounds the hens make inside the nest-holes is a bit scary if you don't know who's making it. It's a low-pitched screaming sound, just like a ghoul or zombie (not that I've ever heard a ghoul or zombie, y'know). A few times, I've been picknicking in the park with the family and enjoyed the sight of a pair of SC2s teaching their two babies to fly. I can't tell you what a lovely surprise it was to see the two chicks emerge from the nest-hole and waddle along a branch beside their mother! On that same day, we spied a Pale-Headed Rosella which had come down to drink from the canal running through the park.
As soon as the weather tones down a bit, I reckon we might do another picnic down at Jesmond Park and see what's there this year.