Young seagull stuck on enclosed balcony

Hi there,

Looking for some advice.

A young seagull appears to have fallen from a higher part of our building on to our enclosed balcony. It does not appear to be at flying age. We have not seen his parents bring it any food and it has not touched any of the food we put out for it. It doesnt seem to be injured as it is fairly active (wandering around and flapping its wings), it also pecks at the glass of our balcony doors a lot.

The balcony is enclosed and has a high guard rail. I am worried that it will not have enough space to fly out as there is not much of a launch area for it. 

Any advice on how we should be proceeding? Is it best to leave it to itself for now or should we be calling somebody?