Tag Archives: Eggs

How long does it take a bald eagle to lay an egg?

An egg in cross section, modified from Romanoff and Romanoff, 1949

How long does it take a bald eagle to lay an egg? We think that female bald eagles begin laying eggs five to ten days after productive mating begins. In 2018 and 2019, Mom laid her first egg about eleven days after copulation went from casual to frequent…and very determined on Mom’s part.  We’ve often seen female eagles take the lead – beak-biting and footing their mates, loudly vocalizing their intentions, and mounting them! You don’t need to be a

When will the eagles start laying eggs?

Egg Calendar

Tik-tok egg clock! When can we expect our eagles to begin laying eggs? If they follow their usual schedules: The Xcel Fort St. Vrain eagles should begin laying eggs in mid-February. Look for laying to start between February 12 and February 21. The Decorah eagles should begin laying eggs in mid-to-late February. Look for laying to start between February 17 and February 23. The Decorah North eagles should begin laying eggs in mid-to-late February. We only have one year of

Peek inside a bald eagle egg: 24 days!

Development of an avian embryo

This blog was first published on March 23, 2017. We reposted it to give everyone a peek inside the eggs. As of this writing, there are two eagle eggs in Decorah. We’re not sure whether the oldest or second oldest egg cracked, but we do know that the youngest is about 24.5 days old, the middle is 29 days old, and the oldest is 32 days old. What do embyronic eagles look they look like as they develop and grow

Peek inside a bald eagle egg: 17 days!

A chicken embryo roughly halfway to hatch

This blog was first published on March 23, 2017. We reposted it to give everyone a peek inside the eggs. As of this writing, there are two eagle eggs in Decorah. We’re not sure whether the oldest or second oldest egg cracked, but we do know that the youngest is about 17.5 days old. What do embyronic eagles look they look like as they develop and grow inside their eggs? Dr. Peter Sharpe from the Institute for Wildlife Studies developed a

Can mice destroy bald eagle eggs?

03/13/19: A mouse under Mom Decorah's tail

Eeeek – mice! We’re getting asked whether mice could or did destroy eggs in our eagle nests. Our answer? A guarded “No”. In North America, researchers have found limited predation by mice in the nests of smaller birds, and none in the nests of birds of prey or larger birds. Researchers have been looking at nest predation for a long time. How do nest location, weather, landscape, habitat fragmentation, and predator-prey/predator-predator relationships impact predation rates? Can nest predation be reduced?

Peek inside a bald eagle egg: 11 days!

Chicken embryos roughly 25% of the way to hatch

This blog was first published on March 23, 2017. We reposted it to give everyone a peek inside the eggs. As of this writing, the first Decorah egg is 11 days, 10 hours old, the second egg is seven days, 14 hours old, and the third egg is three days, 13 hours old. What do embyronic eagles look they look like as they develop and grow inside their eggs? Dr. Peter Sharpe from the Institute for Wildlife Studies developed a table

Peek inside a bald eagle egg: 4 days!

An embryonic bird at 33 hours

As of this writing, the last Decorah egg is 22 hours old, the last Decorah North egg is 9 days, 23 hours old, and the last Fort St. Vrain egg is 12 days, 22 hours old. What do embyronic eagles look they look like as they develop and grow inside their eggs? Dr. Peter Sharpe from the Institute for Wildlife Studies developed a table of bald eagle embryonic development based on work done by Hamburger and Hamilton (1951). While not all

Eggs and cold weather

04/18/18: Mrs. North incubates through the snowstorm

This blog was first published on Wednesday, February 26, 2014. It has been updated to reflect Mom’s new mate and includes some information about the Fort St. Vrain eagles as well. Everyone was worried about the eggs in Decorah back in 2014. Iowa was facing a polar vortex while Mom was laying and incubating eggs. While there have been other cold years, 2014 was one for the record books, with windchills of -50F when Mom laid egg #2. Given that 2019

Do bald eagles delay incubation?

February 14, 2019: FSV

This blog was first published on Tuesday, March 29, 2016. It has been updated to reflect new knowledge and events. Do bald eagles delay incubation? It wasn’t an a question we’ve thought about much, since bald eagles in Iowa usually lay eggs in temperatures under – sometimes well under – freezing! However, 2016 was quite a bit warmer, and the eagles in Decorah and Fort St. Vrain seemed to spend more time off the first two eggs than we are used

Nest chronology: Egg timing!

Second egg for the Decorah Eagles!

This blog discusses the correlation between new mates, temperature, humidity, and egg-timing.  We’ve been getting questions about egg timing. Why did Mom and Dad lay eggs later in 2018? Overall, avian egg-timing in the temperate zone is heavily regulated by the light cycle. As the days begin to lengthen, birds’ gonads swell and produce sex hormones. Around the end of January, our bald eagle pairs switch from infrequent copulation to frequent, highly enthusiastic copulation, putting us on notice for egg

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