Hope that vent is good for a minimum 1 sq ft of ventilation per bird year round, or you have other vents that can be used depending on season. If you have hotter summers, more may be necessary to help let out heat. Even in colder climates, in winter, you'll need to find a way to vent out...
Don't cover up the vents - they want that light to be able to make any last minute adjustments while on roost (or to get back on if they fall off). Also you should always have ample ventilation open for them.