Tag Archives: FAQ

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

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

Birds and Nest-Building

A blackbird's cup nest

When I say ‘bird’s nest’, you know the type of nest I’m talking about, right? It could be a bald eagle’s stick platform high up in the branches of a tree. Or perhaps a peregrine falcon’s scrape in dirt, sand, or gravel on a shallow cliff ledge. Or maybe the burrows that bank swallows and belted kingfishers excavate in dirt, the cavity nests that woodpeckers excavate in dead wood, or the woven nests that orioles and weavers build. When I

Birds in superstition and folklore

Happy Halloween 2022!

The ways in which we watch and learn about birds – HD cameras, high-powered spotting scopes and lenses, and DNA analyzers – are new, but our interest in birds is very old. Sacred and magical birds are common in folklore, oral traditions, and religious texts, including the Bible, the Torah, the Qur’an, and the Bhagavad-gita. It’s easy to say that ancient people lacked a global perspective and scientific knowledge, but a quick search for birds + omens shows that we

On Migration

September 2019: Migrating Birds on the Mississippi Flyway

At whatever moment you read these words, day or night, there are birds aloft in the skies of the Western Hemisphere, migrating. If it is spring or fall, the great pivot points of the year, then the continents are swarming with billions of traveling birds… – Living on the Wind: Across the Hemisphere with Migratory Birds We get a lot of questions about migration. Do the Decorah eagles migrate? Do our Peregrine falcons migrate? Where do they go when they

Eaglet Growth and Development: Week Four

April 19, 2022: DN15 and DN16

We’re writing a series of blogs about the first few weeks of an eaglet’s life. An eaglet spends roughly 75 to 80 days in the nest. For about the first half, it grows and gains weight. For about the second half, it grows flight feathers and starts developing the skills it will need post-fledge. We will focus on week four in this blog. DN15 and DN16 turn 25 and 24 days old today. During week three (fourteen to twenty-one days),

Eaglet Growth and Development, Week Two

April 5, 2021: DN13, left and DN14, right

We’re writing a series of blogs about the first few weeks of an eaglet’s life. An eaglet spends roughly 75 to 80 days in the nest. For about the first half, it grows and gains weight. For about the second half, it grows flight feathers and starts developing the skills it will need post-fledge. We will focus on week two in this blog. In their second week of development, the eaglets will gain roughly two pounds, experience rapid growth in

Eaglet Growth and Development: Week One

March 26, 2021: DN13 eats breakfast!

We’re writing a series of blogs about the first few weeks of an eaglet’s life. An eaglet spends roughly 75 to 80 days in the nest. For about the first half, it grows and gains weight. For about the second half, it grows flight feathers and starts developing the skills it will need post-fledge. We will focus on week one in this blog. What can we expect in the first week following hatching? Like humans, growing eaglets have developmental milestones.

Canada Geese: Precocial versus Altricial

Canada Geese at 24 hours old, Charlo Osprey Nest, explore.org, just prior to the Big Leap

Altricial eaglets rely on parental care until they fledge. But goslings are precocial: capable of moving around, self-feeding, and leaving the nest shortly after hatch. What does that mean? Read on to learn more! Canada Geese and Bald Eagles: Precocial versus Altricial From Stanford University: A precocial bird is “capable of moving around on its own soon after hatching.” The word comes from the same Latin root as “precocious.” Altricial means “incapable of moving around on its own soon after

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,

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