We all want to have a companion bird that lives out its life to the maximum limit. You have read and listened. You have joined group sites and been open to everyone who had something you deemed as sensible advice or a shared observation.
Some of your own responsibility is nothing more than an exertion of common sense and your own surveillance.
Birds drop dead for different reasons. They don't die because they are "small."
A bird that is healthy and playing one minute and dead five minutes later had an "air" problem. He breathed in something that his respiratory system couldn't handle. Whichever, by fume or aerosol or something lodged in his throat, it was incompatible to his ability to receive or assimilate oxygen.
Some deaths are easily recognized - death by poorly-designed toys or your choice of the toy's hanging device, slammed doors, ceiling fans, cats, dogs, ferrets, and active but innocent children.
Some deaths are mysterious ... these deaths haunt us all.
All these things can lead to physical and/or emotional distress.
All small birds shipped in mass, in containers, are high risk for shedding a latent disease.
This is just a blatant reality concerning many small birds… and please know that I am not saying this to be judgmental as I use to raise budgies and still have a deep fondness for them. Small birds, unless bought locally, are usually shipped to pet stores, many in a box. They are not "crammed" and this is not inhumane, it is just a fact.
When you have many young, just weaned babies snatched from their family and home and grouped in a box and flown to the best of pet stores, this is a prime situation for latent diseases to break. How often have you seen a new "shipment" of baby parakeets or canaries in one of the pet chain stores and seen them looking tired and many with their heads tucked into their shoulder? These birds have just survived a major change and upheaval in their young life.
I had a friend who used to refer to all the little birds - finches, tiels, parakeets and lovebirds ... as "cockroaches." She wasn't degrading these small birds, only classifying them as potential "carriers" of some dormant disease.
Remember, a bird can be shedding and pass a disease and not even look sick itself ... but kill another bird next to it. You have got to use good sense and always keep any new bird separate from your existing pet or flock for a few weeks. Wash your hands in-between servicing these cages and if you handle the new bird change your shirt before getting out your other resident bird pets. Treat each new bird as a possible contaminant.
Birds hide their illness so well that we have to really pay attention to small changes in demeanor in order to take the necessary steps to keep them alive.
What you notice in the morning, might be too late to act upon in the evening.