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Tag Archives: Eggs

Egg Colors and Shapes

March 20, 2023 RaptorResource

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? Egg Colors Where do egg colors come from? Once a bird’s egg enters its shell gland or uterus, it is

What Makes Bald Eagles Incubate?

March 2, 2023 RaptorResource

We wrote this blog a year ago. I wanted to revisit it given the events at the North nest this year. Mr. North and DNF have been dealing with intruders for a couple of weeks. Instead of perching near the nest, packing in food, and developing the reserves she needs to lay eggs, DNF is guarding her nest, egg, and mate from potential rivals. After egg number one, her testosterone and progesterone should rapidly decrease, while prolactin, a hormone that

Peek inside a bald eagle egg: 4 days!

February 27, 2023 RaptorResource

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

Announcing: Egg Watch at Decorah North!

February 15, 2023 RaptorResource

Egg watch is on at Decorah North after DNF had us pacing the delivery room floor for over three hours last night! We’ve discussed her most likely first egg date, so let’s take a look at her most likely time. Her schedule looks like this: 2022: DNF laid her first egg at 3:17 PM 2021: DNF laid her first egg at 1:44 PM 2020: DNF laid her first egg at 3:36 PM 2019: DNF laid her first egg at 3:23

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

February 14, 2023 RaptorResource

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

Tick-tock egg clock! Date guesstimates all around our nests.

January 5, 2023 RaptorResource

Tick-tock egg clock! Okay, it’s a little early to start counting the minutes, but here are the days we’ve penciled into our planners for first eggs, first falcons, and ice-out on the Mississippi River Flyway. Get your (RRP) calendars out and feel welcome to make your own best guesstimates. Eggs will be here before we know it! Decorah North I’m saving the afternoon of February 16th for DNF’s first egg! She’s been a remarkably consistent layer date and timewise, although

Finally, an egg at N3!

March 29, 2022 RaptorResource

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

What Makes Bald Eagles Incubate?

February 23, 2022 RaptorResource

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?

January 21, 2022 RaptorResource

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 RaptorResource

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,