Rusty was hit by a car as an adult and admitted to the Raptor Education Group, Inc. in Antigo, WI in 2007?? He is permanently blind in his right eye so he doesn't have binocular vision and wouldn't be able to hunt well enough to provide for a family in the wild.
Iris was admitted to the Raptor Education Group as an adult with a puncture to her right eye in 2006?? Her injury distorted her pupil and damaged her eye enough that it is unlikely she can see out of her right eye, making it doubtful that she could survive well in the wild.
While living at the Raptor Education Group in a cage with many other Great Horned Owls, Rusty and Iris started preferentially "hanging out" together, so Executive Director Marge Gibson thought they would likely make a good breeding pair and offered them to Karla for her research project.
It took several years before their new, spacious home in Houston was built. In the meantime they served as foster parents at REGI for an orphaned owlet in 2009. They moved to Houston in October of 2010.
Although they copulated starting in February of 2011, they did not lay eggs that first year. This probably had to do with not being settled enough in their new home and Scarlett Owl Hara, a wild, unmated female Great Horned Owl that harassed them daily for months, apparently trying to convince Rusty to be her mate.
Scarlett found her own mate in the fall of 2011 and Rusty and Iris laid eggs in late January 2012. Iris incubated dutifully, but the eggs failed to hatch. An examination of the eggs revealed fully developed chicks that died days before hatching. Arnold van den Burg, an expert on unhatched eggs, suspects the eggs overheated based on photos of the unhatched chicks.
In 2013 we let Rusty and Iris raise their three owlets to be completely wild, with only the minimum human interaction necessary. The owlets were released to the wild in the fall after developing their adult territorial hoots, wearing transmitters so we could track their dispersal.
In 2014 we let Rusty and Iris raise their owlets until 2 weeks of age. Then we hand-reared them to become education ambassador owls with a lot of human attention and interaction. We compared their vocal development to the development of the parent-reared owlets to see if it was similar or different due to rearing methods. They have now been transferred over to education permits and will work for the International Owl Center doing educational programs in person. Having them in long-term captivity will allow us to track their voices over their lifetime to see if their territorial hoots are stable or change over time.
Since the goal of this project is research, and research requires analyzing data and publishing, we will not raise owlets in 2015. This will allow time to work on publishing, as well as getting the Owl Center ready to open to the public. Iris's eggs will be switched out for replica eggs after she has finished laying, and we will continue to observe her nesting behavior as well as how long she will sit on the eggs before abandoning them.
Age/Mortality – The first year of life is the hardest to survive for Great Horned Owls and depends heavily on food abundance. Once they reach adulthood survival rates are very good. They have no natural predators as adults, so most owls admitted to rehabilitation centers have human-caused problems: hit by car, shot, electrocuted, caught in barbed wire, caught in leghold traps, west nile virus, poison, etc. Natural causes of death include starvation and hunting injuries.
The oldest known wild Great Horned Owl was 28 years old, but in captivity they can live even longer. A captive female at the San Francisco Zoo turned 50 in 2012.
Weight – Females are bigger and heavier than males, but size varies greatly throughout their range. The largest Great Horned Owls are the pale subarcticus subspecies birds in Canada, with males from 2.3-3.0 lbs and females 3.0-4.4 lbs. Some of the smallest are the pacificus subspecies birds in central and southern California, with males from 1.5-2.8 lbs and females 1.8-2.8 lbs. Iris is a well-fed, fairly large female. She was weighed in the spring of 2011 and was about 4.4 lbs (2000g). Rusty has not been weighed since he came to Houston.
Diet – Great Horned Owls eat almost anything that moves, and will even eat carrion if need be. They are carnivores, however, and don't eat seeds, bread, or anything other than meat. A partial list of food items they have been documented eating includes: hares, rabbits, mice, coots, and ducks (these are generally staples of their diet); skunks, ground squirrels, rats, muskrats, tree and flying squirrels, woodchucks, prairie dogs, raccoons, house cats, very small dogs, porcupines, voles, kangaroo rats, pocket gophers, moles, opossums, chipmunks, shrews, bats, bobcat, weasels, geese, herons, loons, mergansers, grebes, rails, pigeons, starlings, other owls up to and including Great Horned Owls, Osprey, crow, raven, hawks, pheasant, bobwhite, Rhinocerus Auklet, chickens, grouse, shorebirds, gulls, egrets, bitterns, woodcocks, doves, woodpeckers, songbirds, lizards, snakes, frogs, toads, salamanders, worms, crayfish, insects, centipedes, scorpions, suckers, chubs, perch, bluegills, sunfish, catfish, bullheads, and eels.
Basically they eat whatever is handy, and have one of the most diverse diets of North American owls. This helps them to be able to live in a wide variety of habitats, including cities.
Pellets – Like other owls, Great Horned Owls eat fur, feathers, and bones along with the meat and organs. And like other owls, their stomach acid isn't acidic enough to digest the bones, fur, and feathers, so they throw up pellets once a day that consist of these indigestible goodies. (Some other owl species throw up pellets twice a day.) Pellets are coated with a slimy layer of mucous to help them slide up and out.
Nesting – Great Horned Owls, like other owls, are clueless about building nests. They use other available structures to nest in, which include stick nests of hawks and crows; squirrel nests; small caves, ledges or crevices on cliffs or in quarries; sometimes on the ground in the entrance to a den; bridges, power lines, barns and old buildings, large flower pots on balconies, and a variety of artificial nests put up by humans from old tires to laundry baskets.
Eggs and Incubation – They most often lay 2-3 eggs, with incubation usually starting when the first egg is laid. The female develops a brood patch and does the incubation, which lasts 30 or more days. The average number of days is 33.
Fledging – Owlets grow very fast and eat like pigs. They are ready to start "branching" out onto adjacent branches or the side of the nest sometime after 6 weeks of age, even though their head and bodies are still fuzzy. They aren't flying well until 10-12 weeks of age. This is a very vulnerable time of their life.
Can they turn their heads all the way around? Yes and no—it depends on the starting point. If an owl starts with its head in the forward position, it can easily rotate to look directly behind itself. If startled while in this position the owl can crank its head further until it's almost over the other shoulder...in the ballpark of 270 degrees. But they normally don't do more than look over their back under normal circumstances.
But if the owl starts with its head rotated to the back over one shoulder, it can easily turn its head back to the front and then to the back over the other shoulder. So yes, they can easily turn their heads all the way around if they start out facing backwards. This means the can see all the way around themselves without having to move their bodies at all.
On the flip side, their eyes are so large they cannot move them at all in their sockets like we can. So they NEED to be able to turn their heads farther. They accomplish this by having LONG necks (14 cervical vertebrae as opposed to 7 in humans). They just have long, fluffy neck feathers and keep their necks squished down into an "S" shape so it looks like they don't have much of a neck.
All birds have apteria, which are places on their bodies where no feathers grow. These places are covered up by feathers growing in adjacent areas. Noticeable apteria occur on the side of the neck, wingpits, and down the middle of the front of their body.
Bill is the official word for all bird "beaks." Beak is normally used to refer to a sharp or pointy bill (you wouldn't say a duck has a "beak" but you would say a robin has a beak.)
Branching happens just before owlets start learning to fly (fledging), and is when they start to move out from the nest and stand on adjacent branches.
Only female owls develop a brood patch. Many of the belly feathers fall out just before the eggs are laid creating this bare patch of skin to provide easy heat transfer to the eggs during incubation. Male owls do not develop a brood patch so are thought not to be capable of true incubation like in hawks, eagles, and falcons.
Brooding is not the same as inclubation. Brooding is the act of keeping the chicks warm by covering them with feathers. Incubation refers to pressing the brood patch against eggs.
Casting a pellet or throwing up a pellet is normally done once a day by Great Horned Owls. The pellets come out of the mouth covered with mucous and they consist of the fur and bones from their previous meal. Other birds also cast pellets (hawks, eagles, falcons, kingfishers, crows, etc.), but owl pellets are different in that they contain bones (owls can't digest bones well.)
A crop is a food storage pouch located before the stomach. It is found in diurnal birds of prey, but not in owls.
A clutch is a full set of eggs laid by a bird. If eggs are removed, sometimes a bird will double clutch (lay another set of eggs.)
The cloaca or vent is the one and only "out door." It's where the poop, urates, eggs, sperm, and everything else comes out. Copulation is sometimes called the cloacal kiss because the male has to wrap his tail around the female's so their cloacae (plural) can touch and the sperm can be transferred.
Copulation or mating are proper terms for the transfer of sperm from the male to female, but bonding is not a proper term. It's OK to have fun and say "tea time" also, since it certainly sounds like that. Rusty lands on Iris' back to copulate and he is the one that emits the high-pitched squealing sound (a screaming chitter.)
Crepuscular means most active at dawn and dusk. Great Horned Owls aren't strictly nocturnal (active at night), they are generally more crepuscular.
The egg tooth is the little white projection on the top of the bill of a hatching/just hatched bird. The egg tooth falls off a young Great Horned Owl around a week after hatching.
Feaking is wiping the bill on a branch or perch after eating to get the food bits off the bill.
When feathers grow in, they develop and eventually emerge from a feather sheath. The sheaths eventually break up and as the feathers emerge. The shafts of the feathers are filled with blood at this time to provide nutrition for the growing feathers. When feathers are primarily still in their sheaths they are called pin feathers.
Feather tracts are the places where feathers grow on a bird's body. Feathers do not grow everywhere on their bodies, leaving unfeathered areas called apteria.
Fledging is when young owlets are beginning to fly. It takes practice, so this process takes time and they are very vunerable.
GHO is a common abbreviation for Great Horned Owl. The technical and proper scientific abbreviation is GHOW.
Gular fluttering or panting are the terms for when an owl opens its mouth and puffs its throat in and out to cool off when hot or stressed.
Hacking is the term that describes releasing a raptor to the wild while still offering food. Our owlets will be "soft hacked," which means I will simply open the door to the outside world and continue to provide food as long as they want to come back and mooch.
Imprinting is the process of a bird developing its identity when its eyes are first focusing. Normally a bird imprints on its parents or siblings. If raised by humans, they imprint on humans, but retain their natural instincts. They use normal behaviors for their species, but directed toward humans most of the time. Some birds of soft imprints, that only kind-of think they are humans. The other extreme is sexual imprints who want to mate with humans (like Alice.) Rusty and Iris are not imprinted on humans.
Incubation is the act of keeping the eggs warm enough for the embryos to develop into chicks. In Great Horned Owls incubation is only done by the females, as males do not develop brood patches.
Mews is the falconry term for an enclosure for a raptor. I usually don't use this term since most people don't know it. I normally opt for pen, aviary, or enclosure. Sometimes I slip up and say "cage", but this is a word that isn't often used in this context.
Molting is replacing feathers each years. In owls, this happens in the spring through fall. In Great Horned and other large owls, not all of the flight feathers (wing and tail feathers) are replaced each year. It may take 3-4 years for all flight feathers to be replaced in a Great Horned Owl.
Mute is the technical term for poop or pooping, but "poop" is a comfortable word for most people to use also. Slice or slicing refers to the poop or the act of pooping by raptors that squirt their poop way out behind them, like hawks and eagles. Falcons and owls poop essentially straight down and don't slice.
The nictitating membrane is also referred to as the third eyelid. It is a milky blue (in Great Horned Owls) translucent membrane that blinks separately from the regular eyelids. It protects and moistens the eye. You may see it when Iris is feeding the owlets or when the owls are eating.
Owlet is the term for a young owl. Owlets can be nestlings (young ones in the nest) or fledglings (ready to leave the nest or having recently left the nest and are learning to fly.) A juvenile is a young owl that hasn't reached adult plumage.
A pip is the first hole a hatching bird pokes in the shell of the egg.
Preening is the act of running the feathers through the bill to maintain them. Sometimes the bird will first get oil from its uropygial gland and smear the oil onto its feathers. The oil basically waterproofs the feathers, and when sunlight strikes the oil on the feathers, the oil is converted to Vitamin D, which the birds ingest the next time they preen.
Primary feathers are the longest and outermost feathers on the wing and attach to the bird's "hand." They are numbered from the inside out, so the leading primary is P10, and the innermost one is P1.
Rictal bristles are modified feathers densely packed around the bill (beak). They look hair-like and function like mouse whiskers by being very sensitive to touch. When an owl is doing something close-up (like eating, feeding a chick, etc.), it closes its eyes (they are far-sighted and don't see well up close) and just goes by feel thanks to the rictal bristles.
Rousing is the term that describes lifting all the feathers then shaking them like a dog, usually finishing with a head shake. This is only done when the bird is comfortable.
Owls have sclerotic rings in their eyes like all birds and reptiles. This is a ring of bones that is inside the outer membrane of the eye. In owls the sclerotic rings are very pronounced, making the eyes somewhat tubular. The skulls of hawks and owls look very similar, but the pronounced sclerotic rings in owls make the eyes face forward and actually give shape to the face. If you look into the ear of an owl, you see the side of the eyeball and the sclerotic ring is just below the outer membrane covering the eye.
Secondary feathers are the feathers on the wing closest to the bird's body, and they attach to the ulna in the forearm of the bird. The number of secondaries varies by species, and the are numbered from S1 as the outermost secondary (next to P1) to the innermost secondary, next to the body.
Talons are the claws on the ends of each toes (four on each foot.) They are the equivalent of toenails and grow continuously, self-sharpening as they get worn and dulled.
The uropygial gland is also called the oil gland. It is located at the base of the tail on top, where the tail attaches to the body. The oil from the gland is smeared onto the feathers with the bill and tongue during preening.
The International Owl Center advances the survival of wild owl populations through education and research. We plan to accomplish our mission through biological and cultural programs and displays, green building design, citizen-science and other research, international exchange of information, the World Owl Hall of Fame, the International Festival of Owls, and other means.