Fixing a missing vent from the inside.

[NJ C]

Our neighbour let us know that an outside vent on our house had fallen off. It's an awkward location to get to as there's no direct ladder access underneath. I can access the other side of the vent in a cupboard upstairs, so I'm wondering if this is something I could fix/replace from inside? It also seems quite big to me and doesn't have anything between it and the cavity, not sure if this is normal? The location of the vent in the house is close to where an old fireplace used to be, which I'm not sure is related.
Oh, just to make things more annoying we've been hearing a lot of bird sounds from around here so not sure if the thing in the top left is a nest.

 

[Wayners]

Find out if you you need it. Probably don't so block off

 

[noseall]

Our neighbour let us know that an outside vent on our house had fallen off. It's an awkward location to get to as there's no direct ladder access underneath. I can access the other side of the vent in a cupboard upstairs, so I'm wondering if this is something I could fix/replace from inside? It also seems quite big to me and doesn't have anything between it and the cavity, not sure if this is normal? The location of the vent in the house is close to where an old fireplace used to be, which I'm not sure is related.
Oh, just to make things more annoying we've been hearing a lot of bird sounds from around here so not sure if the thing in the top left is a nest.

I'm a bit baffled by the images....

Are they two different (vent) locations?

 

[NJ C]

I'm a bit baffled by the images....

Are they two different (vent) locations?

Nope - last one is the outside view, taken from neighbors window. The rest are inside, before and after removing the vent cover. Tried to get some close ups of inside.

 

[NJ C]

Find out if you you need it. Probably don't so block off

Ah, good point. House is 1920s and that room used to have a fireplace. I'm guessing without that and the fact windows now have trickle vents its less needed.

 

[noseall]

Ah, good point. House is 1920s and that room used to have a fireplace. I'm guessing without that and the fact windows now have trickle vents its less needed.

Block it up and don't forget the insulation.