A year in the life of Astrid
Astrid in a tree cavity
Astrid’s mate, Edward
Astrid is an adult female Great Horned Owl (Bubo virginianus) living in Forest Park in Saint Louis, Missouri. Astrid is the first owl tagged as part of the Forest Park Living Lab initiative. She was captured on October 26, 2021 and expertly fitted with a GPS tracker with help from the World Bird Sanctuary and the Saint Louis Zoo. Locals have seen Astrid in the park with her mate, a male Great Horned Owl named Edward, for many years. In many ecosystems, owls are apex (top) predators. By studying their behavior and their diet, we can understand more about the health of the ecosystem within Forest Park.
Scientists fitting the GPS backpack on Astrid.
Astrid’s tracker is designed to rest comfortably on her back like a little backpack between her wings. By wearing the tracker, Astrid is helping us collect data on urban owl movement and behavior, revealing which parts of the park she relies on. From her data, we have learned that Astrid roosts (spends her days resting) in trees near the Prairie Boardwalk by Steinberg Skating Rink. At nights, she sets out to hunt in the trees just west of the boardwalk and the trees around Jefferson Lake. Interestingly, Astrid visits the sporting areas in the southeast corner of the park, resting on flagsticks in The Highlands Golf Course and on fences and light posts near the Boeing Aviation Fields. Though Forest Park is her “home base”, Astrid also ventures out into the city proper, flying around the hospitals just east of the park and making occasional campus visits to the Saint Louis Community College.
An owl pellet produced by Astrid or Edward.
Owls, like other birds of prey, swallow smaller meals whole – fur, bones, and all! They use their hooked upper beak to tear larger prey into smaller pieces. While the digestible meat passes through their system, all bones, fur, and scales remain in a special organ called the gizzard. Here, muscles press the remains into pellets, which are then regurgitated by the owls and collected by us to study. Owls often produce pellets when they wake up, so we can reliably find them under the trees that Astrid and Edward roost in. We began collecting pellets around the same time that we tagged Astrid, meaning that we are now able to study how these owls’ diets have changed throughout the course of four complete seasons. Once collected, the pellets are brought to the lab where they are carefully dissected. From any intact bones we find, we can then identify from which animal species they may have come. So far, we have found evidence that Astrid and Edward are feasting on mice, shrews, squirrels, and even other birds!
We plan to expand our project in order to learn more about the owls’ roles in the Forest Park food web. Our goal is to tag more owls of various species to get a real “bird’s eye view” of the predator-prey interactions in an urban park. We can compare the data already collected from Astrid and Edward to those of other Great Horned Owls living in more rural areas to understand how life in the middle of a big city affects their behavior. Learn more about Great Horned Owls.