Falcon FAQ

We’ve collected some of our most frequently asked questions here. Have a question you don’t see here? Submit it below on our Ask-a-Scientist form!

Falcon Glossary

Hatch Day Q&A

Banding Q&A

Fledging Q&A

Post-Fledging Q&A

How do you tell the difference between Annie and Grinnell?

Female Peregrine Falcons, like most raptors, are substantially larger than males, so that’s one of the first things we look for. There are also a few differences in coloration between Annie and Grinnell. Annie has a darker gray back than Grinnell and Grinnell has much brighter yellow skin on his face and legs than Annie. Annie also has a streakier breast than Grinnell. One of the easiest ways to identify Grinnell is if you can see his legbands (Annie has none).

Grinnell (left) and Annie (right)

Where did Annie and Grinnell come from?

Annie and Grinnell were first spotted in late 2016 establishing their territory at the Campanile. Bird bands are one of the best ways scientists can learn about a bird’s life. Unfortunately, Annie is not banded, so we don’t know where she came from or how old she is. But we do know about Grinnell’s life history! Grinnell was banded as a nestling by the Santa Cruz Predatory Bird Research Group in 2013 near Martinez, California with his brother, so he’s a local bird.

How long does it take for the eggs to hatch?

Eggs will start to hatch approximately 32-33 days after the third egg is laid. Hatching takes 24-48 hours usually.

I haven’t seen Grinnell in a while, is he ok?

During the breeding season, Grinnell does the vast majority of the hunting, so he’s often away from the Campanile while Annie is caring for the eggs or chicks. When he returns with food for Annie and the chicks, we often won’t see him because he delivers the food to a ledge below the nest on the tower for Annie to grab later.

Is Annie ignoring her first egg?

Bird embryos only develop when the egg is warm – if the egg is cool, the embryo does not grow. Many bird species, including Peregrine Falcons try to synchronize the hatch of their chicks so they’re all roughly the same age developmentally. The difference between a 3-day old chick and a 1-day old chick can be huge! Annie will only partially incubate her eggs until she lays the third egg. She and Grinnell will be keeping a watchful eye on the eggs and occasionally incubating, but she won’t start hard incubation immediately.

What did we do to get falcons to nest on the Campanile?

Annie and Grinnell chose the Campanile as the location for their nest! In totally natural areas, Peregrine Falcons nest on cliffs. When they are in cities, tall buildings can act as perfect stand-ins for cliffs. The Campanile is very well protected from predators and human interference and gives the chicks a safe space to grow and learn how to fly.

When Annie and Grinnell first moved in, they were using an old sandbag for a nest scrape, which caused at least two eggs to roll off. We have upgraded their nesting platform to be a nice gravel tray and shelter, so hopefully we won’t have any more egg mishaps!

Do the bells bother the falcons?

Annie and Grinnell are actually nesting two floors up from where the bells are and are surprisingly well insulated from the sound. Annie can often be seen napping through carillon concerts! You can sometimes see the falcons shake their head in response to the bells, so they do notice them, but they don’t appear to be bothered too much. After all, the Campanile is their choice in nest location!

I sometimes hear people call Grinnell a “tiercel”. What does that mean?

Tiercel is a term used for a male raptor. It is derived from the Latin word for “third” because male Falcons are about one-third smaller than females. You can find a whole Falcon glossary here!

Where are the chicks from last year?

The only way we can keep up with Annie and Grinnell’s chicks is by people resighting and reporting their bands. Here’s what we know about Annie and Grinnell’s chicks:

Year Name Sex Band Number VID Number Electrical Tape Where are they now?
2021 Wek’-wek Male 2206-82983 81/AN (Left) Blue (Right Leg) Fledged
2021 Kaknu Male 2206-82984 82/AN (Left) Yellow (Right Leg) Fledged
2021 Fauci Male 2206-82985 83/AN (Left) Red (Right Leg) Fledged
2020 Poppy Female 1687-29761 24/AM (Right) None Unknown
2020 Sequoia Male 1687-29762 01/AM (Left) Yellow (Right Leg) Unknown
2020 Redwood Male 2206-82967 U/71 (Right) Blue (Left Leg) Unknown
2019 Carson Male 2206-82959 U/48 (Left) Blue (Right Leg) Unknown
2019 Cade Male 2206-82960 U/51 (Right) Yellow (Left Leg) Unknown
2018 Lawrencium Female 1687-29748 11/AM (Left) None Nesting on Alcatraz
2018 Berkelium Male 2206-82947 U/27 (Left) None Unknown
2018 Californium Male 2206-82946 U/46 (Left) None Unknown
2017 Fiat Female 1687-29740 03/AM (Right) None Unknown
2017 Lux Female 1687-29741 04/AM (Left) None Died after striking a window

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