Birds hardly ever die instantly of natural causes, when they are sick to the point of dying they don't perch in the trees anymore and are even less likely to be flying. A dying bird will usually try to hide under a bush or plant when it is to weak to fly - flying takes a tremendous amount of energy. In towns and suburbs cats do get most of them. You have no idea just how many birds are taken (dead or alive) by the friendly household puss. Foxes clean up a fair amount of dead ones. Those that are not scavenged by mammals are rapidly disposed of by insects, fly maggots etc. and the fragile bones disappear in a few days by visits from many beetles and snails.

Other birds eat them too. A sparrowhawk eats an average of three sparrows a day and will probably have most success with older weaker birds or the fledglings which have not yet learned to keep out of the way. I think (and I'll probably be corrected!) that there are an estimated 16,000 sparrowhawks flying around above us in the UK. That works out to an awful lot of sparrows per year. There are plenty of other birds of prey that will happily pick off all kinds of smaller birds.

not just birds. all dead things, mice rats, etc. There is a certain species of beetle [forget it's name will search] that specialises in dragging dead stuff away to be eaten later.. undertaker bug or something... or is this an urban myth?

Yep thought so..[Why, then, when we walk in the woods do we see so few that have died? Part of the answer to this lies in the astonishing activities of the tiny burying beetle, genus Nicophorous - sometimes called the sexton beetle, or the undertaker beetle. The beetles can bury an animal the size of a mouse in just a few hours. There are nineteen known species of Nicophorous is North Carolina, carrying on their work under cover of darkness] LINK; http://www.lib.ecu.edu/NCCollPCC/Critters.html

hi is it usual for someone to find two dead birds in there garden one other day one today just a bit worried sorry