Hi Lisa,

The primary concerns with utilizing this area for a vegetable garden are as follows:

Will the soil support the type of vegetable you desire to grow? To address this concern get a soil sample.  Poultry manure can be high in nitrogen and if it is too high it can have an adverse effect on the plant/vegetable  

Are there any remaining bacteria that could have an impact on food safety from the birds being present ?

Salmonella and other food born pathogens can be in bird droppings. To address this, the area should sit dormant for a period and it would be best to allow the soil to go through a heat, this would reduce the presence of pathogens in the soil. If there is excessive manure on the surface, you may want to remove this, then rototill the area, cover with plastic or a tarp to assist in heating the soil (especially since we are entering cooler weather).  If you will be growing leafy vegetables that will come in direct contact with the soil and not be cooked, this is where the greatest concern would be from a food safety standpoint. If you are able to follow the above mentioned process, you should be able to grow with minimal concern.