Master builders: Most birds construct nests for one simple reason, but that doesn't mean they build only one type of nest

摘要

Birds that become parents face a fundamental challenge. They must provide warmth to their developing young, yet they may not retain their embryos internally, like most mammals, since they are bound by an overarching requirement to maintain minimum weight for flight. The strategy for most birds is to keep their embryos warm outside the mother's body by incubating. To do so, they surround their embryos with nutrients and a special shell that is porous enough for air to flow through, strong enough to support the weight of a sitting parent, and thin enough to allow the chick to break out at hatching.