Nesting
Hummingbird babies weigh 0.62 grams when they hatch. This means 3 newly hatched hummers would weigh less than one American dime. Without feathers their skin is fragile and they need a soft nest that protects them as they grow. The little hatchling's mother had the instincts to know how to built this nest.

Tiny hummingbird in the nest. Photo: Creative Commons amslerPIX CC BY 2.0