12/23/2025
Love is in the nest! Our eagle-eyed camera operators spotted a copulation on camera yesterday: our first on-camera copulation at the North Nest since April 4.
What triggers copulation? Let’s back up to the summer solstice in mid-June, when the days are at their longest and the great seasonal wheel of the year is turning slowly. A bird's go**ds regress, its reproductive hormones ebb, and a new hormonal phase takes over. Depending on age, species, pair bond status, parental status, and migratory behavior, it may respond by decreasing fledgling care, flocking, increasing food intake, storing more body fat, and/or leaving its summer home.
At my house on the 45th parallel, we start looking for flocks of starlings and blackbirds in August. On the Flyway, waterfowl numbers begin ramping up in early September. And among territorial non-migratory Bald Eagle pairs, the change sparks nest-building, which reinforces the pair's bond.
As courtship deepens, nestorations ramp up. Last year's nest is buried beneath piles of sticks and heaps of corn husks, corn stalks, and fluffy grass. Male eagles bring food gifts, couples perch and vocalize together, and pairs dig, scrape, and mold soft materials to form a cradle for their eggs. They progress from working and perching together to pecking, footing, body brushing, and displaying, which further reinforces their bond and eventually leads to copulation. Big nests are sexy! https://www.raptorresource.org/2025/11/13/birds-and-nest-building-2/
After the winter solstice, days lengthen, eagle go**ds swell, reproductive hormones start flowing, and copulation increases. Last year, copulation began on December 9, although it didn't really ramp up until January 28: 17 days prior to DNF laying her first egg. We'll be looking for - and counting! - copulations to help us predict laying this year. Stay tuned!