seagull apparently is very oily and not very tasty but could sustain someone in need. I think the St Kilda islanders used to net and eat them when the islands were occupied but they had little else to eat. but these were seagulls fed on wild fish, not on town scrapheaps so they may taste different.
anyway, seagulls are protected so you can't just go out and shoot one to eat! councils are allowed to cull them but they use poison bait so no way would you want to eat one of those!