What is growing there now?Question: what should I sew to replenish the yard not in use?
What is your goal?
Plants the birds can eat?
Plants they can't destroy to protect the soil from eroding?
Deep rooted grasses well established can help with that.
Maybe some of each?
Keep in mind the soil may be compacted and inundated with high levels of nitrogen and phosphorous(I think)...that can be a challenge to getting anything to grow well.
It would also help to know.....
Where in this world are you located?
Climate, and time of year, is almost always a factor.
Please add your general geographical location to your profile.
It's easy to do, (laptop version shown), then it's always there!