Tag Archives: Reproduction

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

How long do peregrine falcons live?

Peregrine falcon Michelle at fifteen years old

How long do peregrine falcons live and/or reproduce? This question was inspired by a discussion in the Midwest banding group last week. Jackie Fallon of the Midwest Peregrine Society shared a Facebook post about Hunter, a 21-year old male peregrine falcon who was rescued in Toronto, Canada. Hunter is the oldest known wild-producing falcon in North America: https://www.facebook.com/Canadian-Peregrine-Foundation-149280041803853/. The Manitoba Peregrine Falcon Recovery Project followed up with the story of Princess, a 19-year old falcon who was rescued in Winnipeg,

How long does it take a bald eagle to lay an egg?

An egg in cross section, modified from Romanoff and Romanoff, 1949

How long does it take a bald eagle to lay an egg? We think that female bald eagles begin laying eggs five to ten days after productive mating begins. In 2018 and 2019, Mom laid her first egg about eleven days after copulation went from casual to frequent…and very determined on Mom’s part.  We’ve often seen female eagles take the lead – beak-biting and footing their mates, loudly vocalizing their intentions, and mounting them! You don’t need to be a

What is up with our eagle Moms?

05/09/19: Mom and DM2

We first blogged on this subject on April 30, 2014, but we’re asked about Mom’s behavior every spring. Wondering where the love went? This blog is for you! We’ve had several questions and comments about our eagle Moms. Why are they so demanding? Why are they mad at their mates? Why are they so mean? While I can find snippets of behavior that seem loving to human observers – shared incubation duty, mutual nest defense, and tandem feedings, to name

Do bald eagles delay incubation?

February 14, 2019: FSV

This blog was first published on Tuesday, March 29, 2016. It has been updated to reflect new knowledge and events. Do bald eagles delay incubation? It wasn’t an a question we’ve thought about much, since bald eagles in Iowa usually lay eggs in temperatures under – sometimes well under – freezing! However, 2016 was quite a bit warmer, and the eagles in Decorah and Fort St. Vrain seemed to spend more time off the first two eggs than we are used

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