Tag Archives: Circannual clocks

When will our eagles lay eggs?

January 26, 2025: Mr. North and DNF duetting

When will the Decorah North, Trempealeau, and Fort St. Vrain eagles begin laying eggs? Mark your calendars as follows! It looks like the lead-up to eggs has started at the North nest. Mr. North and DNF have copulated almost every day since January 24 and DNF was very interested on the one day they didn’t. This is very similar to 2024, which again, puts egg number one around February 15. We’re also seeing solicitation, footing, and duetting. More on eagle

Love is in the Nest! Bald Eagle Courtship and Copulation

January 22, 2025: Nest building, beaking, and bonding

Love is in the nest! We are guesstimating that DNF will lay her first egg on or before February 16. If her egg is going to be fertilized, the two need to copulate a lot. What does bonding look like so far? Prior to December 7th, Mr. North and DNF last copulated on April 9th. We saw more copulation in December of 2024 than December of 2023 (nine versus three) and, prior to the onset of egg-laying, slightly more in

Getting ready: Fall nestorations!

Annual Daylight Length, Decorah IA

Why are eagle couples in Decorah working on their nests and bonding right now? Among non-tropical birds, many activities (reproduction, molt, migration) are linked to daylight length. We’ve primarily discussed the photosensitive period of bird life here, when daylight lengthens, gonads start swelling, and human watchers start counting the days until eggs are laid. However, birds also have a photorefractory period that in many northern birds begins slightly prior to summer solstice in mid-June. Gonads start shrinking, a new hormonal