Canary died, but how??

[Nay]

I'm very sorry you lost your bird. I will say that in the UK canaries are regularly kept in aviaries outdoors, even when it gets cold (sometimes with a heater). The usual advice is to keep them above 8 Celcius /43 F, which is much colder than their native environment. I wouldn't keep like that, but I've seen how they can be pretty hardy, based on the ones I've seen outdoors here in Scotland. I'm not sure if the cold was the reason especially if they are used to being there [although warmer temperatures would help].
If the waterer is as dirty as you say maybe there is a husbandry issue, or the bird wasn't expecting the different dimensions of the waterer and didn't recognize the change before it was too late.

Their waterer was in need of a deep clean so I got them a temporary waterer which was a small jar, which they are very familiar with.

It might be hard to know exactly what happened. In the UK this weekend we are having a severe weather situation (Storm Dennis). OP's initial suggestion that a shock from a sound outside could have spooked the bird is certainly possible. Indoors my house you can hear the wind howling and the branches flying around outside, its incredibly noisy and violent. Will need to sleep with earplugs tonight. I think its a very good idea you moved them from the windows, it is incredibly loud and chaotic out there. Stay safe!

 

[clucking with my chicken]

My father always kept canaries, in outside avaries in the Breacon Beacons and regulary had to break the ice on the water in winter for them. They adapt to their environment so please do not feel you were neglegent in any way. Whatever it was that she/he died of will be something you may never find out, these things happen sometimes, as sad as it is.

thank you so much, all day I left bad for him, we have been really busy lately so what should I do with my remaining bird, we have no family that are able to look after them

 

[clucking with my chicken]

I’m keep with the spooked bird because he was such a wimpy little guy. Such a lovable little bird.