Oriole Eggs and Babies

Imagine being locked in a tiny, oval-shaped room for two weeks. At first the walls are cushioned with a goopy liquid, and you're stuck in the middle. There is no food, but you don't notice. You never feel the least bit hungry. The room seems huge at first, but as the days go by, the walls seem to close in. Or is it that you're growing bigger? You're cozy and comfortable at first, but after 10 or 11 days, you start feeling cramped. The goopy walls have been drying up somehow, and they now feel a little hard. You've been curled up for so long, and suddenly you yearn to stretch. You twist your body around, maybe trying to find a more comfortable position, and instinctively scratch on the walls with a hard bump on your beak. Somehow that gives you a satisfying feeling, and you do it some more. Your eyes are closed, but you sense a tiny ray of light seeping in where you've been scratching. You stretch, and with a crack, the walls suddenly break apart. In an instant the room is flooded with light. You're tired, but determined. Little by little you stretch and twist, and suddenly the walls of the room fall away. You find yourself snuggled against a warm tummy and some hard round shapes. But one of them suddenly falls apart, and suddenly you're right next to a bald, wet, little baby oriole. A baby oriole just like you!

Size and Shape

Baltimore Oriole Eggs
Photo copyright by Todd Ratermann

Look at these oriole eggs, and think about the magical process taking place inside each one. Notice the shape. A few eggs, such as those of owls, are spherical, but most are more "egg-shaped." Do you think this makes it easier for the female when it's time to lay the eggs? Might that be the reason why eggs have no squared or jagged edges?

Hungry Hatchlings!
Once oriole babies hatch, they're hungry!! The parents both feed them, coming to the nest a total of about 13 times an hour from sunrise to sunset. The babies grow from about 2 grams at hatching to about 34 grams when they fledge,11-14 days later.


Try This! Calculations

  • The average weight of an oriole egg is 2.99 grams. The average weight of the empty shell is 0.20 grams.
    1. How much does all the "stuff" inside the egg weigh?
    2. If a newly-hatched oriole weighs 2.00 grams, what do you think happened to the other 0.79 grams? (Click here for the answer)
  • Let's assume it takes 12 days for a baby oriole to reach 34 grams in weight. If an 8-pound human baby gained weight at the same rate, how much would the human baby weigh in 12 days? (Click here for the answer.)