If you look through the history of human buildings all the way back to the first huts, it seems that insulation was more of a lucky afterthought than a conscious decision. Sealing out drafts and getting out of the elements were the primary motivators for our earliest ancestors; it wasn’t until bands of people settled down into an agriculture-based society with permanent dwellings that houses could evolve in a meaningful way.
Luckily, at some point, builders realized that they could control the temperature of their homes by manipulating the materials used in construction. Persian ice pits constructed in 500 BC were made specifically to store snow and ice for long periods of time, and were formed from sand and mortar to be resistant to heat transmission. Natural insulators gave way to sophisticated materials made especially for construction, and nowadays there are hundreds of different materials and forms to choose from. However, we humans are late to the game; the Megapodiidae family of birds have been building insulated nests for thousands of years.
Meet the Megapodes
The megapodes are a taxonomic family consisting of seven genera of medium-to-large birds. The name ‘megapodiidae’ translates to “large foot”, referencing their heavy legs and impressive claws; other nicknames include ‘incubator birds’ and ‘mound-builders’. These avians look fairly similar to turkeys, with an oval body, bright neck ruff, and feather-free head. Some can fly, but others are exclusively terrestrial; unable to build their nests in the safety of the treetops, megapodes must build ground-based shelters to keep their eggs safe.
Since megapodes are solitary birds, they cannot consistently incubate their eggs with their own body heat; each mother must find her own food, even after laying. So instead the megapodes bury their eggs, and use thermodynamics to expertly control the temperature of their developing offspring. To accomplish this, they dig a hole and fill it with rotting leaf matter and other compost. The eggs are laid on top of the compost, and the entire mound is covered with a thick layer of sand. The compost produces heat as it decomposes, which keeps the eggs warm; the sand layer prevents this heat from escaping.
A megapode watching her eggs will constantly adjust the mound’s size, removing or adding compost depending on the stages of decomposition and resultant heat output. She can accurately maintain the temperature so that the eggs don’t overheat or freeze. Biologists are stumped as to how megapodes innately know the thermodynamics of insulation; it’s tough for birds to keep eggs incubated at the best of times, and these creatures manage to manipulate a large external structure to accomplish the task. More intriguingly, the baby megapodes do not learn this skill from a mother; they are solitary from birth, and the mound-building knowledge seems to be a reflex.
So if you ever find yourself stumped about whether to choose fiberglass batting or spray foam insulation, remember: you can do spray foam insulation quickly and easily. The megapode has rotting leaf matter to work with; you can fill in that crawl space with polyurethane spray foam, no problem. Sometimes, a bird-brained approach turns out to be a puzzling and fascinating part of the world we live in.
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