The birds get a lot of articles, and the topic is well known to locals. I believe there is a trust that organises some conservation effort for them, but my Google-fu couldn’t find anything online about it.
There are hundreds that nest at the end of the spit. You can see how close to residential areas it is, a short walk: https://www.google.com/maps/place/Southshore,+Christchurch/@...
The reserve gets quite a lot of foot traffic, many locals walking the beach, and some visitors in summer (being at the end of a cul-de-sac helps reduce visitors). It would not surprise me if the end was cordoned off in the future, although I presume that would require a marine reserve status or something as I’m not sure under what circumstances the government can just fence off foreshore areas.
Aside: I recently found one dolphin vertebra, which would be legal to have if I notified the right people. “you are entitled to collect bones, teeth, ivory or ambergris that have already separated naturally from a dead marine mammal provided DOC is notified as soon as possible and are given details of the time, place and circumstances under which these items are found.”[1]. You can’t chop out a bone from a carcass: “if anyone removes any part from a dead marine mammal this also may be interpreted as taking that mammal ... liable to imprisonment for up to 6 months, or a fine of up to $250,000” + $10k per animal. The actual law[2] says: “by any person who finds or collects bones, teeth, ivory, or ambergris that have already separated naturally from a marine mammal if that person, as soon as practicable, notifies the Director-General or an officer of the find, and gives details of the time, place, and circumstances under which the find was made” so notify both?
Aside 2: I found an albatross wing on the beach a few months ago - much longer than my arm. I am pretty sure that it is highly endangered and illegal to even pick that up[3][4]. However a friend is taking it in to the museum where there is someone that can decide what to do with it. I have found dead penguins in Dunedin and Kaikoura, and a penguin wing at Brighton.
[1] https://oceanlaw.co.nz/wp-content/uploads/2016/07/MarineMamm...
[2] https://www.legislation.govt.nz/act/public/1978/0080/latest/...
[3] https://www.tepapa.govt.nz/sites/default/files/tuhinga.25.20...
[4] https://www.stuff.co.nz/environment/118796601/fisheries-hook...