Help!! How do I get rid of BIRDS who got into our ventilation hole?

Hi, we own two story house down here in Ontario and there are several ventilation holes on sides of the house.
On two of them (one from kitchen ventilation, another from 1st floor washroom ventilation), outside cover of the hole is flip up time. (cover opens from outside by flipping up, made of 3 plastic covers, hole size is 4 inch)
I have no idea how but there was small mouse making problem at first then there seems to be multiples of birds LIVING THERE.
It must be dark there in the hole and I have no idea why they are living there making noises.
Someone said they might have nested there for child birds to get ready to fly, etc.
Anyways, they are making way too much noises that I need to do something about it.
For the cover, since they learned how to open the flip and get in, I plan to put some additional cover to prevent that to open in the future.
But how do I get rid of them?? Trap, poisin, glues all might catch them but they will decay in there giving me bigger problem.
Any recommendations?
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If babies are there wait till they leave then remove the nest and cover it with screen, If no babies and its a powered vent maybe a bucket of amonia under the vent and turn it on.
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snipped-for-privacy@gmail.com wrote:

Patience. Two, maybe three, weeks. Chicks will be gone.
Momma bird is just trying to make a living, and I'm sure she appreciates the warm, dry, safe nesting place you provided.
In the meantime, if the cries of baby birds begging for their suppers bothers you, there's always earplugs.
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