Injured seagull

Hi, 

I am after some advice about a young seagull. (Quite large in size but with grey feathers) It has been in the yard at work since Monday. There do not seem to be any adults around. It has a limp and doesn’t fly away when approached. I have put water down, and some food but it doesn’t seem interested. I have rung a local wildlife centre this morning but they aren’t taking birds in due to avian flu. I am not sure what to do. Any advice much appreciated

thanks in advance