What happened to my birds?

Please Help me understand? My mother has 10 parakeets in her apartment. she has 2 cages and they stay open and the birds come and go as they please. well at this time 1 set of her birds is nesting so their locked up with their eggs in one cage. The other 8 were left to hang out My mother went on vac. she left sunday. My brother checked on them tue, they were fine. I came thur at 6pm and found 6 dead. It was so so weird they had no food left but water was clean and good. found some seed on the floor. when looking for the other two i count find i found them hiding. I'm just trying to understand how i colud of lost all these birds. in just a short time. Could they have died cause they ran out of food but still had fresh water?

 

If the apartment was too cold or too warm that could have caused this, Also if your mother did not fill the food bowls before she went away this would mean they could have gone longer than 3days without food, but i can not see that being the reason.

Its more likely they have injured themselves or eaten something that is toxic to them.
The only way to know what has happend is by taking the dead birds to an avian vet and asking for them to do necropsy on them all and see what caused this.

Birds should never be left out of there cages unsupervised as this is when accidents happen.

Sorry i could not be anymore helpfull.

Mike