Why Don’t You See Dead Birds Laying Around?

bird-374072_640As you walk around the city or countryside, you might occasionally spot a dead mouse, rat, or squirrel. Driving down the highway, you regularly see road-killed raccoons, opossums, or some other mammal. But how many dead birds have you seen? Maybe an occasional road kill, but that’s all. Why is that? Birds are light in weight, thin skinned, have little fat, are covered with feathers, and have some hollow bones, so they are less dense and weigh a lot less than comparable sized mammals. When a dead bird hits the ground, it is almost immediately invaded by small decomposers in the form of bacteria and insects. Vultures and coyotes might also take part in the feast, but the tiny organisms are usually the quickest and most efficient. Being thin and light, a small bird decomposes into an unrecognizable blob in about a day and will disappear in three. A larger bird will take a bit longer, but a small mammal, say a rat, might continue to exist in recognizable form for a week or more. A road-killed hawk or owl will be reduced to nothingness in a few days to a week while a fat, thick-skinned, heavy boned raccoon might lie as a blob on the shoulder of the road for two weeks or more.

Birds also float. If they land in a pond, puddle, or lake, they are exposed to the air and the scavengers and decomposers and rarely fossilize, compared to mammals that tend to sink and get covered by sediment. This explains why the fossil record of birds is so poor compared to other vertebrate groups.

There is a scientific paper published in 1903 by M. Cline. Now, this is before we knew much about flight, or even feathers. Ms. Cline stated, in all seriousness, that birds are able to fly because they take a deep breath of air, making themselves lighter than air (ok, already the argument loses credibility) and fly off. Her proof is that the piles of feathers you occasionally observe in the field or forest are the remnants of the birds that took too deep a breath and exploded! These feather piles are, of course, the aftermath of a poor bird meeting up with a predator. Raccoons, foxes, or opossums will consume the muscle, but leave the inedible parts – the bones and feathers. The bones are rapidly consumed by rodents who want the calcium and beetles ingest the feathers quickly as they are mostly protein.

The only time I have seen a number of dead birds is around bodies of water, after an epidemic of avian cholera hit the waterfowl populations. One of the weirdest things I ever experienced, though, is standing under a juniper tree talking to a colleague, discussing some subject of global importance, no doubt, when a swallow fell from the tree and landed in my outstretched hand, dead.

By the way, you can’t get West Nile Virus from handling a dead bird, but it’s still not a good idea to pick one up.


2 thoughts on “Why Don’t You See Dead Birds Laying Around?

  1. Dr. Lederer,

    This is a question I have pondered and am so glad to have given Google a chance on this. I am an artist working mostly in clay (and some printmaking) and birding images are frequent in my work. I of course have had fanciful explanations always looking for metaphor in nature. Perhaps no less credible than Ms. Cline’s but certainly less violent. I was thinking about this recently because I saw a perfect circle of feathers but no body in one part of my garden as if a whirling dervish of a bird had spun off its feathers. It’s grey feathers looked like a mourning dove. The on the same day a tiny bird with yellow and grey feathers on my back steps. It sat there for days. Surprising because of the numbers of scavengers and predators that abound.

    In any case your explanation is as rich metaphorically as any. I thank you for your post. And if you have an idea as to why the little bird was still there – barely with any evidence of decomposition days later please speculate. It is February but we have had both 80 degrees one day and a low of 25 just a few nights later. For some reason many people think my last name is yours though it is an entire syllable shorter!

    1. Your description of circle of bird feathers reminded me of a fanciful theory I just saw presented as an answer to the question of where birds go to die on the website Quora. It took me a minute to understand answerer Mehul Soni’s verbose response, but basically this person was reporting someone else’s a theory that birds have an innate knowledge of when they will die (kind of like how they know when to fly south for winter), and that when it’s time for their life to come to an end, they simply fly up and up until the atmospheric conditions cause their bodies to naturally disintegrate. I think it’s probably more likely that old or diseased birds hide until they are eaten by predators or die and quickly decompose, but I prefer the flying up and up theory and will imagine it to be the true one from now on. 🙂

      Here’s where I read about that theory:

Leave a Reply

Your email address will not be published. Required fields are marked *