sorry for your loss
seal it in something before you burry it. I used a metal box from a first aid kit. anything that will seal will be ok. zip lock baggie, tupperware ...
I usually put deceased animals in a plastic bag surrounded by paper towels in a cigar box and bury the box a few feet down.
And i am terribly sorry to hear of your loss, cockateils are such nice birds,
i am sorry for your loss..how old was your cockatiel...mine lived to 21... i think your little friend will have no negative impact on the eco system... he needs a little special place for you to remenber him.,,maybe a nice little flower to mark the spot..