Minus 1: Tree for Two

Hummingbirds typically lay exactly two eggs. One scientist studied 77 Ruby-throated Hummingbird nests. He found 86% of the nests with two eggs (66 nests had two eggs, 10 nests held only one egg, and one nest had three eggs).

Q. Think of some reasons why hummingbirds almost always lay exactly two eggs. (Answer below photo.)

A. One egg is not the best number for hummingbird nests. If anything happens to one baby or the egg doesn't hatch, all the work and energy the mother put into building the nest and incubating will be lost. But more than two eggs take too much energy from the mother. She would have to sacrifice more body heat to the eggs, and so much food to feed three babies, that she might grow too weak before they were ready to be on their own. A hummer nest with three babies could possibly raise all the babies successfully if weather conditions were great and food abundant--but it's a very big risk.

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