Tag Archives: FAQ

Peek inside a bald eagle egg: 24 days!

Development of an avian embryo

As of this writing, there are two eagle eggs at Decorah North. The youngest is just over 22 days old and the oldest is just over 25 days old. We anticipate that the oldest egg will hatch on or around the morning of March 23. . 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

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

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

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

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

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