Natural Selection Step 1: Overproduction of Offspring
I need to have at least 2 clutches of eggs this summer.
Hummingbirds are at risk of predation
This is the story of "Rosy" the Ruby Throated Hummingbird." As it was spring time Rosy knew that it was time to lay eggs. All the creatures in the woodland were busy doing the same thing, preparing for offspring. Excitement was in the air.
Overproduction of offspring means some will survive.
Rosy knew that she needed to lay many eggs as early in the season as possible. If she could produce one clutch of eggs, then there might be time to lay a second clutch before the summer season ended.
Natural Selection Step 2: Variation
Why would Rosy want to have so many babies? Well, Rosy knew that the sneaky fox who was always hanging around would love to to have Rosy, or her eggs, for a meal.
Rosy knew that having a large clutch of eggs (or even a second clutch in the season) increased the likelihood that some of her offspring would survive.
So rosy laid her eggs (5 this time) and incubated them for 11 days until they hatched. She noticed when they hatched that not all her chicks were the same. Some were larger than others and vocalized more. Others started moving around the next more quickly than she would have liked.