By Karla Bloem
Executive Director International Owl Center
Rusty and Iris came to live at the International Owl Center in 2010. Both of these Great Horned Owls had vision in only one eye, preventing them from being released to the wild. They were perfectly capable, however, of breeding in captivity. The Owl Center acquired permits for these owls to study Great Horned Owl vocalizations, including the complete vocal repertoire, the development of the territorial hoot in young birds, and the heritability of territorial hoot characteristics…all things that couldn’t be studied in the wild.
In 2011 Rusty and Iris weren’t settled yet and were harassed regularly by Scarlett Owl Hara, a wild unmated female. In 2012 they laid fertile eggs but the owlets died in the eggs before hatching. In 2013 they hatched out three owlets: Pandora, Patrick, and Patience, who were eventually released to the wild wearing transmitters, after they developed their adult vocalizations.
In 2014 Ruby and Rupert were hatched. They were removed from their parents at two weeks of age to be raised as education birds, since Alice the Great Horned Owl was getting up there in years and needed some younger birds to start taking over programs for her. Raising them with humans also allowed a look at how owlet vocal development compared between owlets raised by humans and owlets raised by owls that know they are owls (Rusty and Iris).
The next two years Rusty and Iris were not allowed to breed for various reasons related to permits and plans for any offspring. In the meantime, Rusty’s vision declined to the point that Christmas lights were installed in the aviary so Rusty could see well enough to fly properly after dark. More offspring needed to be produced soon, while Rusty is still able, to get a better feel for how hoot characteristics are passed from parents to offspring.
Due to a late permit application, Rusty and Iris’s first clutch of eggs had to be removed this year. Iris sat on fake eggs while waiting for the permit decision. One egg in the first clutch was infertile, possibly an indicator that Rusty was also getting up there in years.
After a bumpy and agonizing wait, the permit was granted for Rusty and Iris to breed. The fake eggs were immediately removed and Rusty and Iris got busy on the next clutch. They copulated 10-12 times a day and after about two weeks they laid two more eggs (while being harassed by a wild, unmated female Great Horned Owl named Lilith.)
Since fertility was a concern, it was VERY wonderful to hear an owlet chittering in one of the eggs on Friday, March 31! (Owlets can begin to vocalize when they poke into the air sac at the end of the egg just before they start hatching, one of the specific things the vocal study is recording.) Saturday morning a pip appeared, but the fuzzy little owlet didn’t finish hatching until early Sunday morning.
The eggs were laid just over three days apart, which is normal for Great Horned Owls, so the next owlet could start vocalizing in the egg on Monday. It wasn’t heard. By Wednesday morning there was still no sound and no pip. Was the second egg infertile?
Then around 10 a.m. on Wednesday, April 5, Iris stood up and a little pip was visible, with a little beak seen moving in the hole. This owlet didn’t mess around: it was completely out of the egg by 6:20 p.m., although owlet #2 wasn’t visible until after 9 p.m..
Young owls grow EXTREMELY fast. They’ll be ready to start flying around by mid to late May, so if you want to see them as tiny babies, go to www.InternationalOwlCenter.org now and click on the Rusty and Iris cam link to get your daily dose of cuteness. The cams have an online chat room too, so you can ask the moderators any questions you might have.
This breeding project is the first study of the vocal development of ANY owl species in the world, and you can be a part of it. Simply pay attention while you watch and submit an online form if you see Iris off the nest, hear the babies “hooting” in their tiny voices, or other exciting things. Unlike most other cams, you’ll be able to watch these owlets grow to maturity since they are in captivity.
Because little funding is available to study common species, this research is funded entirely by private donations, and most of the work involved is done by volunteers across the USA and Europe. You can provide financial support for the project by making a donation through the Owl Center’s website (above).