Fort St. Vrain Eagles and Blogs

What are feathers? What is molt?

Feather Follicle

Eaglets go through two molts and three feather stages in the nest: natal down (and molt), followed by thermal down (and molt), followed by juvenile feathers. As of this blog, the Decorah North eaglets are shedding the very last of their natal down and their thermal down is rapidly being replaced by juvenile down and feathers. We thought we would blog a little more about feathers to celebrate!  When we think about feathers, we tend to think about their qualities

Bald eagle tongues and beaks!

March 25, 2024: DN17 and 18 eat.

We know that bird beaks are specialized for feeding and daily tasks. Birds of prey have strong, curved beaks with sharp edges to help them tear meat. Falcons specialize even further, adding a tomial tooth to help them kill prey. Dabbling ducks have tiny, comb-like structures on their beaks to strain small animals, insects, and plants from water and mud, while piscivorous ducks have saw-like structures to help them hold on to struggling fish. But what about bird tongues or,

March 8, 2024: News and NestFlix from around our nests!

March 6, 2024: Mr. North appears to be shedding a tear, but it isn't a tear or extra-renal salt removal (which is pretty cool, TBH). It's a remarkably well-placed raindrop!

Congratulations to the Fort St. Vrain Eagles on their third egg! We haven’t passed the solstice yet, but spring has sprung: almost all of the birds we watch are busy laying eggs, tending eggs, protecting territory, courting, and/or copulating right now! We’ve been working hard and hope to have a few cool surprises for everyone in the weeks to come, but in the meantime, kick up your feet, grab a beverage, and soar into the weekend with our NestFlix raptor

What is a brood patch?

March 30, 2018: Mrs. North's brood patch

Daylight length, or photoperiod, strongly influences hormone production in birds. In the northern hemisphere, our story begins shortly after the winter solstice in December. As daylight length increases, a cascade of hormones causes birds’ gonads to swell in preparation for reproduction, egg-laying, and incubation. In this blog, we’ll discuss the role the brood patch plays in incubation and determining clutch size. How do bald eagles keep their eggs warm in subzero temperatures? They apply heat via a special area of

Leap Year eggs for two eagle couples!

February 29, 2024: A second egg for Mrs. T!

Congratulations to two eagle couples! Ma and Pa Jr. laid their first egg at Xcel Energy’s Fort St. Vrain nest tonight, and Mr. and Mrs. T laid egg #2 at Trempealeau! Ma frequently lays three eggs, so if she holds to her usual schedule, look for egg #2 on March 3 and egg #3 on March 6th. We don’t know how many eggs Mrs. T lays since this is our first year of data, but we’ll be watching! Tulsa has

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

February 20, 2024: NestFlix, News, and What’s Coming Up!

February 19, 2024: DNF rolls her eggs and gently settles over them.

We have a NestFlix Megaroll for everyone tonight, but I wanted to go through our calendar before we get started. Here’s what’s going on! Thank you so much for watching, sharing, learning, and caring! We hope you enjoy the videos as much as did! Decorah North Eagles February 20, 2024: Beautiful view of both eggs at shift change – We finally got a glimpse of the eggs! They look lovely nestled in their bed of soft golden grass: the

How do eagles stay warm in cold weather?

January 23, 2023: HD sports eye-cicles on a frosty morning in Decorah. An icy fog left everything coated with frost

Each species experiences the world differently and eagles have capacities that are far different from ours. How do Bald Eagles survive an Iowa winter without adaptive clothing and central heat? A cold January morning coated our eagles in frost and left watchers wondering how Bald Eagles survive an Iowa winter. In general, wintering animals – including humans – need to retain body heat, stay dry, and take in enough calories to support winter’s increased energy demands. We humans put on

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