There are estimated to be around 160 million birds in the UK with a lifespan of two to five years. Why do I never see a dead one?
Based on these figures, one small bird dies in the UK every second. There are several reasons why you seldom see a dead one.
Deceased small birds blend into the background: you could be within 5 metres of one and easily miss it, especially as dying animals crawl into hidden spaces like under bushes and fall asleep, forever. Many are also eaten by predators and all that remains is a small circle of feathers, quickly used by other animals as nesting material. Finally, nature disposes of corpses very quickly, with mammal scavengers, insects and their larvae, bacteria and fungi recycling them within a few days.
You only see dead animals on roads where they haven’t had a chance to crawl away and scavengers can’t easily eat them. But even on roads, you see magpies and crows dodging cars as they do exactly that.
As a keen observer of nature, I, too, have long puzzled over what happens to all the dead birds, although I do periodically find dead, but undamaged, small birds in the garden.
I have got into the habit of feeding the local wildlife, and have found that anything edible left in the garden overnight is gone the next morning. My camera trap tells me that most of the food is taken by foxes, some of the rest by cats and a small amount in the summer by hedgehogs. Rats, mice, voles and shrews are present, but rarely show on the camera. Anything left at dawn appears to be taken by crows.
Any wild animal weakened by old age, illness or injury that ventures out of hiding is easy meat for its predators and will be killed and eaten before it can die of any health problems. You therefore won’t see the body.
In Almost the Last Word in the 20 November issue, it was pointed out that the “most environmentally friendly way to deal with a dead body is to eat it”. This is also why we don’t see dead birds – they are eaten, in nature’s efficient and sustainable way of recycling and tidying itself up. Thanks to foxes, red kites, raptors, fly maggots and bacteria, nothing is wasted. I am not suggesting we dispose of human bodies this way, but it is food for thought!
There may be around 160 million breeding birds in the UK, but the actual number of birds is far greater. From the amount of breeding attempts a pair of each species typically makes, plus how many chicks fledge from each attempt, it has been calculated that there may be more than 400 million individual birds in the UK in autumn.
A pair of blue tits may fledge 10 chicks, and to keep the population stable, only two chicks need to survive; the others must die, so we should be knee-deep in dead chicks.
One reason why we aren’t is the “clean-up crew”, variously known as Sexton beetles or burying beetles. I monitor nest boxes each spring, and if I happen to check a box a few days after chicks have died, I often encounter these beetles. They smell the decaying flesh, fly to the carcass and begin removing material from under it. A week later, there will be no chicks visible – they will now be under the nest material. Once the body is buried, a female beetle lays eggs in it, and the larvae feed on it after hatching.
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Soon after a bird dies, scavengers like rats, foxes, and carrion-eating birds will assist in disposing of its remains. The bones are a good source of calcium, and they will eat almost everything. The feathers that are left will soon blow away and rot.
Once dead, a bird decomposes fairly quickly. They have hollow bones, very little body fat, and air sacs strewn throughout their skeleton to help with breathing because they must be as light as possible in order to fly. All of this makes a bird very fragile. A dead bird can decompose naturally in two or three days thanks to flies, insects, and bacteria. This process won’t take long.
Actually, very few birds in the wild pass away from old age. They are an essential component of the food chain because they consume fish, amphibians, insects, and smaller birds, which are then eaten by larger birds and mammals. This explains why they have so many children and why they start breeding at such a young age. For instance, the majority of garden birds in Britain reach sexual maturity at the age of one year, but they only have a year or two more of wild life left. The same species will live a lot longer in captivity.
Generally speaking, birds do not usually die while in midair or perched on a branch. We would be in serious trouble if they did. Similar to humans, a bird that dies from natural causes will, prior to passing away, likely be ill, injured, or elderly, which will cause it to move less and possibly not fly at all.
In the United Kingdom, there are more than 150 million living birds that are constantly flying, swimming, and hopping around.
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