BeakersBro, your sisters friends bird probably died because he or she was sick and no one realized it. Some illnesses, so little is known about them that the only symptom of that illness is "sudden death". In other words, it's most often not found out until the bird is already dead.
It's a bit past 8pm here and I just checked the birds room temperature. If it was accurate (don't know, had to move a digital thermometer from a different room, and takes a bit to adjust), then the temperature read at 63.5° F. It's only 8pm, it's going to get colder! If I remember, I can recheck in the morning!
I know that I've recorded temps as low as 52° or 54° F, at night. In the winter, the temps usually rise to the mid 60's to lower 70's during the day (or warmer, if unusually warm winter), but fall again at night.
I've had Casey, my very first cockatiel, for 12 years and nearly two months. That's the longest out of any birds in my current flock. The longest bird I've had after her is my bourke parakeet at 11 years this month. She's supposed to be around 16-18 years old now. She is pass her life expectancy by 1-7 years. If cold temperatures kill birds, then my entire flock should be dead, especially these two, since they have endured cold temperatures (and even pretty hot ones!) the longest.
I personally don't believe that drafts kill birds. I agree that a sudden temperature change for a long period of time can indeed kill a bird if they can't adjust to the temperature change, but drafts and short temperature changes isn't going to kill a *healthy* bird. I've taken my mitred conure outside in the winter and he happily sat out there preening himself, squawking and I even had him flying. He was unfazed. My cherry headed conure used to love to sit in front of the AC in the car when I took him places. In the Spring, Summer and possibly Fall months, if it's warm, I leave the window(s) open 24/7 to allow fresh air to move around the room.
If you think about wild birds and what they have to deal with... constant temperature changes, wind, etc, it doesn't make sense that a simple draft is going to kill a bird. That's like saying that if you're sick, you should stay inside the home with the windows kept shut, when in fact the air inside our homes can be more polluted than the air outside!
If you think about it in the sense of a canary in a coal mine, then yes, that makes sense! Because that "draft" of air may have toxic chemicals (methane or carbon monoxide) in it.
Birdie Buddy Habitats
Air
“...it surprises most people to learn that the air at home , where we eat and sleep and spend most of our time, is often dirtier than the air on highways or around industrial plants”
UC Berkeley Wellness Letter
- October 2004