Low light scope?

[Muskett]

Glass that can do it on its own is too expensive and not often air rifle parallax compatible. A huge objective is just so bulky. I wouldn't go beyond a 30mm tube and 50mm objective as they are bulky enough.

For dark area lofting birds a power rifle mounted torch that can focus the beam can cut the gloom if necessary. Its the cheapest option. These LED power torches aren't very big and can be had for under £40.

One other option is to go NV. A Pard 007 with a good compatible scope would do it with ease. MTC and Hawk have scopes that are ideal.
If it was a dedicated rifle for rats and lofting pigeon then the Pard 008 would do it too. Day or night around the farmyard they do it all, just all in digi.