Tag Archives: Weather

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

Eggs and cold weather

04/18/18: Mrs. North incubates through the snowstorm

This blog was first published on Wednesday, February 26, 2014. It has been updated to reflect Mom’s new mate and includes some information about the Fort St. Vrain eagles as well. Everyone was worried about the eggs in Decorah back in 2014. Iowa was facing a polar vortex while Mom was laying and incubating eggs. While there have been other cold years, 2014 was one for the record books, with windchills of -50F when Mom laid egg #2. Given that 2019

Nest chronology: Egg timing!

Second egg for the Decorah Eagles!

This blog discusses the correlation between new mates, temperature, humidity, and egg-timing.  We’ve been getting questions about egg timing. Why did Mom and Dad lay eggs later in 2018? Overall, avian egg-timing in the temperate zone is heavily regulated by the light cycle. As the days begin to lengthen, birds’ gonads swell and produce sex hormones. Around the end of January, our bald eagle pairs switch from infrequent copulation to frequent, highly enthusiastic copulation, putting us on notice for egg

How do eagles stay warm in cold weather?

04/18/18: Mrs. North incubates through the snowstorm

Iowa bald eagles nest in surprisingly cold weather. How do they keep themselves and their eggs warm? Unique body features and changes in physiology and behavior help bald eagles maximize energy gain, minimize energy loss, and incubate eggs in cold temperatures. To maximize gain, eagles forage in groups, gorge food, and increase the assimilation of ingested food energy. To minimize loss, they become sedentary, seek protective microclimates, and reduce night-time body temperature. Put simply, eagles keep warm by using the