Bald Eagles: Egg to Week One!

Question #1: About how much do eaglets weigh one week after hatch?

Four and six day old eaglets in Decorah
The Bald eagle may have the fastest growth rate of any North American Bird. They go from roughly 3.2 ounces / 90 grams - about the weight of 18 nickels - to roughly 16 ounces / 453 grams, increasing their weight five times over in just seven days!

Question #2: About how much do newly hatched eaglets weigh?

Bald eagles weigh roughly 3.2 ounces at hatch (Bortolotti, 1984) - or about the weight of 18 nickels!

Question #3: True or false: Bald eagles need to eat immediately after hatching!

Sorry, the answer is false! Just before hatch, the eaglet draws the remaining yolk into its stomach via a cavity that is still open. The cavity closes, leaving the yolk sac scar. The yolk provides nourishment for at least 24 hours after hatch.

Question #4: When does an embryonic eagle’s heart begin beating?

Ten stages of embryonic development
Sorry: a bald eagle's heart begins to beat inside the shell roughly 72 hours after an egg is fertilized. Think of that the next time you see a recently laid egg!

Question #5: When does an embryonic eagle develop its egg tooth?

Ten stages of embryonic development
Sorry: a bald eagle's egg-tooth forms about 11 days after an egg is laid!

Question #6: What eagle body part achieves maximum growth the first ten days after hatch?

D25, D24, and Mom
Sorry! An eaglet's culmen - the dorsal ridge of the upper mandible - is its most rapidly growing body part in its first week after hatch. Since food is the root of all else besides, it isn't surprising that eaglet beaks get developmental priority!

Question #7: On average, bald eagle eggs are:

Bald eagle eggs
Sorry! Bald eagle eggs are about 2.9 inches long and 2.2 inches wide. Learn more about eggs here:

Question #8: What is an Eagle’s temporary ‘belly button’ called?

Bald eagle egg yolk sac scar
Sorry! The answer was 'Yolk Sac Scar'!

Question #9: Can hatchling bald eagles thermoregulate?

Sorry! Natal down is adorable, but it doesn't provide thermal protection. An eaglet's second coat of down (thermal down) starts replacing natal down at about 10 days. They begin thermoregulating, or maintaining a consistent body temperature, at 10-15 days of age.

Question #10: What is the protrusion on the tip of a newly hatched eaglet’s beak called?

Mom and D24
Sorry, the answer is egg tooth! The egg tooth helps an eagle cut through its shell as it hatches. The sharp protrusion wears away in about three to four weeks.