Tag Archives: Eggs

Finally, an egg at N3!

March 28, 2022: D2 in N3. Photo by Mark Worcester.

What has been going on with Mom and DM2 this year? RRP staff and volunteers have been monitoring Mom and DM2 at N3 and the hatchery, and we have a pretty good record of their whereabouts with boots-on-the-ground observations and appearances on the hatchery cams. We have documented her standing in the nest for long periods of time, but she didn’t begin incubating until sometime between Robin’s observations on Sunday, March 20 and Dave Kester’s observations on the morning of

Egg Colors and Shapes

The Chicago Peregrine Program inspired me to write a quick blog on the colors and shapes of eggs. Bald eagles have white eggs, peregrine falcons have eggs that range from light cream through brick red, and red-tailed hawks have pale eggs that are lightly splotched with brown. How and why do the birds we watch lay differently-colored and shaped eggs? In general, female birds inherit egg colors and patterns from their female parents. Egg-shell is made primarily of calcium carbonate,

Peek inside a bald eagle egg: 11 days!

Chicken embryos roughly 25% of the way to hatch

What do embryonic 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 bald eagle eggs hatch in 35 days, the stages of development look something like this… What happens between the third and the 11th day? When we last touched on the topic, our embryonic eagle had

Peek inside a bald eagle egg: 4 days!

An embryonic bird at 33 hours

As of this writing, we’re still waiting for eggs at Fort St. Vrain. The first Decorah North egg is seven days old and the second is four days old. What do embryonic eagles look like as they grow and develop 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 bald eagle eggs hatch in 35 days, the

What Makes Bald Eagles Incubate?

February 21, 2022: North Nestoration Follies!

I loved watching Mr. North incubate eggs through today’s snowy weather. He turned his head out of the wind, closed his eyes to protect them from the blowing snow, and fell asleep as the nest rocked gently back and forth. What makes normally active birds like hawks, falcons, and eagles spend so much time sitting on eggs? Hormones, egg production, and broodiness As daylight length increases, birds’ gonads swell. Both sexes produce testosterone, although male birds produce more than female

Why do bald eagles lay eggs in ice and snow?

Egg-laying Map

Why do the Decorah and Decorah North eagles lay eggs in ice and snow? A lot of you – especially those of you who also watch the Florida eagles – are curious about bald eagle egg timing. Wouldn’t it be better to delay egg-laying until mid-March or early April? We’ll unpack the question by starting with a few facts. An Overview of Bald Eagle Nesting Bald eagles don’t all nest at the same time. In the southeastern United States, especially

Nothing Goes to Waste

March 16, 2021: Ma and Pa Jr. on the nest, Fort St. Vrain, Platteville CO

Xcel Energy’s Fort St. Vrain eagles rode the big storm out last weekend. Despite an astonishing twelve or so inches of snow, Ma kept the eggs covered through most of it. Male and female eagles both incubate eggs, but females usually cover the nest at night and through bad weather. A female eagle’s larger body size and brood patch helps her stay still for longer periods of time and apply more heat to the eggs and young beneath her. Unfortunately,

Eagles, ‘menopause’, and a new mate at Xcel Energy’s Fort St. Vrain plant

Avian Reproductive System, From Handbook of Bird Biology, Second Edition

Has Ma FSV entered ‘menopause’? This blog was going to be focused on eagles and ova, but Elfruler, our original DE lead mod and a long-time chronicler of bald eagle nests, noticed that the male had a band on his right leg, not his left. A new eagle has replaced Pa FSV. If you’d like to learn more about eagles and ova, please read on (TLDR: Ma FSV has not entered menopause). Thanks to Elfruler for her observations and Donna

Courtship, copulation, and other things romantic!

February 5, 2020: Body brushing - Mom and DM2 stand wing to wing in the nest

This is a traditional Valentines Day post for us, but we decided not to wait this year…just in case one of our eagle pairs lays eggs early! Bald eagle courtship Bald eagles are famous for their whirling nuptial flight, but eagle courtship includes any activities that establish a new pair bond or renew an existing one. At our Decorah, Decorah North, and Fort St. Vrain nests, courtship usually begins in early October. Bonded pairs start working on their nests by

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

« Older Entries