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Scientific Inquiry
(W)hooo Lives in the Box?

(W)hooo Lives in the Box?

by Kimberly Dare

Pictured above is one of the owl boxes on the UCSC Farm, built near a kiwi vine. 

The children looked at me with curious eyes as I pointed upward and whispered, “Who do you think lives in that box?” One child guessed a squirrel but another felt that the animal needed wings to reach the top. I replied, “Hmm, it must be a bird if it has wings. Why am I whispering? Could it be sleeping right now? What bird might be sleeping?” My students took a minute to think and shouted all together, “Owls!” 

Owls come in many shapes and sizes as there are over 250 species around the world, living in different habitats like agricultural fields or thick forests. Most live in natural habitats like trees or caves, but some rest in human-made places like owl boxes or barns.

As predatory birds, owls might prey on mice, gophers, shrews, voles, smaller birds, and fish — depending on the species. Hunting happens at night since most owls are nocturnal. Owls have remarkable hearing and great night vision to make hunting easier. With unique wings for a silenced flight, owls use their sharp talons to capture or kill their prey. A prey is consumed immediately or stored in a hidden place for later consumption. 

Females lay anywhere from one to fourteen eggs during the breeding season, depending on the food supply. Baby owls (nestlings or owlets) hatch in four to five weeks, but not all babies will survive to adulthood. Nesting sites play a major role in an owl’s survival which is why people should be educated if inspired to build their own owl box. 

UCSC Farm Owls

UC Santa Cruz has an organic farm, the Center for Agroecology and Sustainable Food Systems (CASFS), at the bottom of its campus which commonly deals with rodent pests. Rodents like mice, gophers, shrews, and voles will eat farmers’ plants, dig up dirt, and spread diseases. The farm tries to reduce the harmful rodents through pest control by having cats and metal cage traps. Another method is by attracting natural predators, animals who feast on rodents as part of their regular diet. Farmers design gardens in a specific way, grow certain plants, and build owl boxes to purposefully attract predators. 

The UCSC Farm has two owl boxes. The first box overlooks the main farming field near a kiwi vine. This first owl box inspired neighborhood residents to build a second one on their private residential area, but it is still close to the farm. Both boxes are several feet above the ground for easier nesting. Plans to build a third box are in development.

An owl box in a private residential area.

Unlike metal traps, owls are a natural way to control rodent pests. Owl boxes are man-made, but owls ultimately choose where to rest based on natural instincts. Loud areas, like major cities, scare owls away. Since the farm is quiet and away from heavy traffic, owls continue to live in the boxes and help farmers control rodents.  

Barn owls mainly live in the UCSC owl boxes, arriving around February and staying until autumn. A single barn owl can eat two to three rodents per night, while a whole family can eat up to ten! While it is commonly barn owls that live in the owl boxes, other owl species—like great horned owls—have been reported elsewhere on the UCSC Farm. Audio clips of both barn owls and great horned owls’ calls at the UCSC Farm have been recorded by the Santa Cruz Predatory Bird Research Group.

Owls as Educational Ambassadors

Building owl boxes provides a lot of opportunities to learn about nature. On the UCSC Farm, a non-profit organization called Life Lab teaches gardening and life sciences to young children. Owl boxes are a popular and exciting spot to educate children about owls’ lives and their roles at the farm. In addition, owl pellets,an owl’s regurgitated food remnants usually containing rodent fur and bones, are great learning tools for children. With a bone identification sheet (similar to the one showcased), children discover and identify different bones  as they dissect pellets with their bare hands. Amy Carlson, a long-time staff member at Life Lab states, “Kids in our programs love to visit the owl box and look underneath for pellets. We identify the bones in the pellets and talk about how the owls help the farm by eating animals that eat our crops. So the owls not only help the farm, they also help kids learn about ecology and sustainable farming!” With owl boxes, children simultaneously act as explorers, scientists, and detectives. 

Copyright Carolina Biological Supply Company.
Used by permission only.

An Owl Box of Your Own

Anyone can build an owl box similar to the ones at the UCSC Farm. Building owl boxes are generally useful for pest control and educational purposes; however, people should first consider if owls would be safe nesting in their box. Are there a lot of cars or a major highway nearby? Do people use pesticides or other harmful chemicals on plants or pests? (Rodenticides can poison owls which is why nearby areas should be rodenticide-free.) Is it generally noisy in the area? Are there any other factors that may cause harm to owls? If “yes” to any of these questions, then an owl box may do more harm than good.  

However, if all answers are “no,” then an owl box would be safe. If possible, find out what owl species live in the area by researching online, asking wildlife officials, or contacting local organizations. Pre-built boxes and owl box construction instructions are also available online. Afterward, determine the best place for box placement. Boxes should be placed in an open area, away from houses with bright lights. While it depends on the species, barn owls should have a box on a high pole that is eight to twenty-five feet tall to avoid animal intruders eating their eggs and young. Be aware of any exposure to weather conditions (high winds, severe weather, extreme heat, etc.) that may pose a safety risk. Once everything is carefully set — wait, observe, and soon you can enjoy the presence of owls. 


1. Owl Research Institute. (n.d.). “About Owls.” Retrieved from https://www.owlresearchinstitute.org/owls-1

2. NestWatch. (2019). “Barn Owl.” Cornell Lab of Ornithology. Retrieved from http://www.nestwatch.org/learn/all-about-birdhouses/birds/barn-owl/

3. Kaufman, K. (2019, October 22). “Barn Owl.” National Audubon Society. Retrieved from http://www.audubon.org/field-guide/bird/barn-owl

4. World Of Owls. (2019). “Food and Hunting.” Retrieved from http://www.worldofowls.com/food-and-hunting/

5. Life Lab. (n.d.). “Field Trip Training Manual.” Santa Cruz.

6. Bluebirds of San Diego County. (2019). “Attracting Barn Owls.” California Bluebird Recovery Program. Retrieved from http://www.cbrp.org/SDBluebirds/owl.html

7. Glucs, Z. (2019). “Owl Recordings.” Santa Cruz.

8. Carolina Biological Supply Company. (n.d.). “Owl Pellet Bone Chart.” Retrieved from https://www.biologycorner.com/resources/Owl_Pellet_Bone_Chart_grid.pdf

9. Hunt, B. (2018). “Attracting Owls to Your Backyard.” Owl Research Institute. Retrieved from http://www.owlresearchinstitute.org/attracting-owls-to-your-backyard

10. Barn Owl Box Company. (2017). “Barn Owl Biology.” Retrieved from http://www.barnowlbox.com/barn-owl-biology/

11. Arnold, K. (n.d.). Retrieved from publicdomainpictures.net/pictures/50000/nahled/barn-owl-portrait-close-up.jpg

12. Maria, H. (2018, October 16). “Great Horned Owl Portrait.” Retrieved from https://pixabay.com/photos/owl-great-horned-owl-portrait-3745861/

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