Tag Archives: Molt

How do we know falcon Zooey’s age?

March 10, 2021: Zooey from the back

How do we know that falcon Zooey is two years old? Peregrine falcons have two distinct age-related plumages: juvenile and adult. Juvenile falcons have heavily barred underparts and brownish topsides (“brown birds”), mature falcons have pale undersides with black-barred bellies and blue/slate topsides (“blue meanies”), and two-year-old falcons like Zooey have a mix of adult and juvenile feathers. I love this stage! Tail Feathers (Retrices) Like all peregrine falcons, Zooey has twelve tailfeathers that are numbered one to six from

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