Winter is coming

[cocotiel]

Since winter is just around the corner here in my country, the lows tend to be around 2 to 5 degrees at night and in the day time it is around 8 to 10 degrees celsius on a very cold day. It’s going to be my cockatiel’s first winter of its life and of course my first winter taking care of it too. As I have heard cockatiels do survive well in the cold but I’m just not sure to what extent it is true.
My concern is what measures do I need to take in order to keep my baby warm?
Also I would love to know what to expect from my bird behavior wise and the signs to look out for just in case I need to take some extra measures to keep it warm.
Currently Coco’s cage is placed in the tv hall which is a large space. Would it be helpful if in the winter I shift the cage to my room which is smaller and will be less colder? We don’t use heaters in the house because warm clothes are enough for us but at night we do use an electric heater for a bit to make the room warm and turn it off before sleeping, just letting you all know in case the information is important.
I’m planning to start covering Coco’s cage with a warm blanket once the nights start getting colder for now but I have no idea what to do next. I also found out that we can put a bulb inside the cage which will act as a source of heat but that seems very dangerous to me for some reason.
I’m so worried and I’m hoping to be able to get some helpful advise from all of you amazing people.

 

[Mizzely]

What is the temperature in the house? That's the important bit it can get to -20C or colder here but that's obviously not the temp in my house! We usually keep it about 18 in the house, but it can get as low as 15 at night.

As long as changes are gradual, (not going from hot to cold immediately) they usually do pretty good

 

[MommyBird]

I don't know what country you are in but I have been using "Sweeter Heater" for many years. The XS size is quite enough used in conjunction with a partially covered cage.

 

[cocotiel]

I’m not sure what the temperature inside the house is but it is definitely not as cold as outside. The house is still cold though since heaters are not common (more like not necessary) here so I don’t know whether it will be okay for my bird or not or if I need to do something else about it.
The changes in the weather are gradual and around December and January it gets extremely chilled specially if it rains but of course it’s never as cold as -20 degrees where I live.
I am in Pakistan and it doesn’t snow in my city here. Just the occasional rain.

 

[flyzipper]

My concern is what measures do I need to take in order to keep my baby warm?

I’m not sure what the temperature inside the house

As @Mizzely wrote, I'd suggest getting an indoor thermometer and placing it near Coco's cage.
The actual temperature will determine what measures you'll need to take, or it may reveal no action is required and put your mind at ease.

I understand you're trying to be proactive, but there's no sense wasting money on solutions might be unnecessary.

If long shipping times are an issue where you live, the suggestion from @MommyBird is a good one for supplementing warmth to Coco's cage, or an even smaller solution is the K&H warmer that's more localized and would be something they would perch close to if they wanted additional warmth.

Even if you choose to add a heater, I would still suggest adding a thermometer to monitor the temperature to avoid the potential of creating a large difference between their cage temperature and the rest of their environment.