Tag Archives: musing

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

Could HD or HM be one of Mom and Dad’s offspring?

HD (left) and HM (right). HD stands for 'Hatchery Dad' and HM stands for 'Hatchery Mom'. We could change the nomenclature, but that is what we are using now. We can clearly see the ID cues mentioned in previous pictures: HD's smaller beak, guyliner, cere markings, and whiter head, and HM's larger beak, and flatter, darker head. She is also much larger and has a small circular mark on the right side of her face. Glogdog: "Since HM is larger, her folded flight feathers fold lower near her tail's end, and HD's flight feathers fold shorter near the tail tip." A fantastic ID tip for ID'ing them from behind!

Could HD or HM be one of Mom and Dad’s offspring? Mom and Dad’s oldest eaglet turned 14 years old this spring. Since bald eagles tend to nest in the region they were born, it’s possible that at least one of them was produced by Dad and OM, or Dad and Mom. But male and female eagles have slightly different nesting dispersal patterns, which makes male HD the more likely offspring choice. Natal dispersal in birds is defined as the

What is going on with the Decorah Eagles?

February 17, 2021: Mom mantles a rabbit at N2B

What is going on with the Decorah eagles? We saw them maybe 13 or 14 times in January and DM2 delivered nesting materials just twice – a far cry from the nestoration activity we’re used to this time of the year! But we suddenly started seeing a lot more of them on February 14. Mom and DM2 are hanging out on and around the nest, removing snow, and refurbishing the place with new cornhusks, sticks, and rabbit fur. Are they

Do female eagles experience menopause?

November 15, 2020: Nestorations at N2B

We’re getting a lot of questions about eagles and what might be called menopause this week. Many of you want to know if female bald eagles stop laying eggs due to age-related changes in their bodies – the avian version of menopause. Is Mom disinterested in DM2 because she’s done with eggs? The short answer is ‘No’, but I want to unpack the question a little further. Human menopause is very unusual. Unlike the vast majority of animals, women can

Eagle #musings: SW Florida, Fulton Trio, Mississippi Flyway

November 2, 2020: Bald eagles on the Mississippi Flyway

A number of you have contacted us about the SW Florida and Trio eagles. While these aren’t our nests, they raise interesting questions about eagle social, nesting, and bonding behavior. I hope this blog helps answer your questions! Southwest Florida Last year, Harriet and her mate M15 reclutched after their lone eaglet, E14, died of rodenticide poisoning on January 15. While Bald eagles at this latitude normally hatch in late December or early January, E15 and E16 hatched in late

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