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Bald Eagles Fact of the Day

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At one week of age, the hatchling becomes a nestling, and continues to grow extremely quickly. By the end of its first week, the nestling may weigh around 16 ounces. At around 9 to 11 days, the secondary down (or thermal down) begins to appear.  This down is much darker, thicker, and woolier than the natal down.

For April 11, 2020

Eaglets spend most of their first week of life gaining weight. The eaglets aren't able to thermoregulate* yet, so depending on the weather and temperature, they have spent a lot of time under Mom or DM2.  We've been observing them eating, sleeping, scuffling, and growing stronger each day as they interact with one another.  They will grow from about 3.2 ounces at hatch (about the weight of 18 nickels) to about one pound in their first week.  This is an increase of about 5 times their weight in just in seven days!  Who is counting out 18 nickels now to see how much they weighed at hatch?  :)

Today, D34 and D35 are six days old and D36 is three days old!


*thermoregulate means regulating their own body temperatures.  That takes about 15 days.   

Periods of Growth:

 eaglet: anytime from hatch to about 10 weeks from leaving the nest.

 hatchling: first week ,

 nestling: first week to fledge

, fledgling: while perfecting fledge,

 juvenile: when 1st set of feathering grows in and for the first year,

 Immature or subadult: after 1 year until adulthood.

 Some of these terms can overlap.

Behaviors in raptors are: imprinted, innate (or instinctive), and learned.  A raptor's behavior comes from these 3 components and their interactions.  Imprinted behavior happens early in life and is basically unalterable, as is innate behavior.  Learned behavior can be modified during the life of the bird.

Bald eagles do not have vocal chords, so the sounds they make are done by passing air through the bones in their neck.  The sound comes from an area called the syrinx where the windpipe is separated going to the lungs. They have 3 main vocalizations: contact calls between mates, peal calls which are territorial calls and begging calls from the eaglets.

Bald eagle calls:


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