Dinnertime For Our Birds of Prey
By Jennifer Meikle, Environmental Educator
At Woodcock, we currently have three birds of prey as animal ambassadors. All our birds can no longer fly due to wing injuries from being hit by cars. I was covering feeding one day, which involves placing a combination of dead thawed (originally frozen) rats, mice, and chicks in the bird enclosures for their dinner. Starting with Click, our Barred Owl, I place her mice on the stump which basically serves as her plate. She watches me from a distance with her large eyes; she’ll come back to eat those later on, often when no one is around. I move onto our next enclosure, placing rats on the stump for our Great Horned Owl, Hooty. Like Click, she will eat her meal when it’s quiet and she’s alone. The floors of the two owl enclosures are littered with owl pellets, the regurgitation of the indigestible parts of their prey, like bones, feathers, and fur. This is an amazing thing that owls do, and you’re lucky if you ever find an owl pellet while on a hike or exploring nature. Owl pellets tell an interesting story about what they have recently eaten. It’s like a little treasure trove of information and dissecting owl pellets with the students who attend our programs is always a huge hit.
Finally, I move onto our last bird enclosure, containing our newest addition to Woodcock Nature Center, our Red-Tailed Hawk named Cheyenne. Cheyenne is completely different from our owls, not only because she is a hawk, but also because she has a very outgoing personality (paired with a huge appetite)! Cheyenne comes so close to the door that she’s practically touching it with her feathers, head cocked looking for her yummy chicks. With a gloved hand, I hold out the first one and she snatches it with a talon, quickly hopping away to gulp it down. She does the same with the next two chicks and her feeding is over almost as soon as it began. The ground in Cheyenne’s enclosure does not appear to have pellets of any kind. Yet while eating her meals, she will throw back a mouse or chick with fur, beak, and all. Despite being an educator for the last few years and a long-time nature and animal lover, I wondered for the first time in my life why do owls need to spit up all the indigestible tough parts of the animal that they eat, while a hawk does not?
This question inspired me to do some research about this topic. Hawks can digest bones! I know that seems obvious, given that if they are eating them and not regurgitating, they must be digesting them somehow, but it is fascinating to me, nonetheless. The bones are an important part of a hawk’s diet because they provide nutritional value. By consuming and digesting the bones from their prey, their bodies extract calcium for bone growth, maintain a strong beak and talons, and obtain essential amino acids, which are all extremely vital to the health of the hawk! Being able to consume the entire prey is also advantageous because they can utilize a wider variety of food sources and are able to extract more nutrients from the prey they do catch. Digestion begins in the hawk’s gizzard. The gizzard is a muscular organ (also known as the ventriculus) that grinds the bones into smaller pieces, allowing them to be digested even further in the hawk’s second stomach, called the proventriculus, where digestive enzymes soften the bones and digestion continues. Hawks store food in their crop, so that they don’t have to work on digesting it all at once. More food will move into the stomach only when it’s empty. Owls’ bodies don’t do this. When they eat a meal, it goes into their stomach all at once, which is why they can’t fully digest the bones and tougher parts of the prey.
While the entirety of their prey is beneficial for a lot of reasons, there are some risks too. The bones can cause gastrointestinal issues, especially if sharp ends and edges cause complications which can lead to internal injuries and infections. While a hawk’s body breaks up and digests the bones of its prey, they do actually regurgitate a pellet, or cast, which contains the other indigestible parts, like feathers and fur. Their pellets differ from owls (which contain bones and teeth) because of their difference in digestive systems. The cast composition also varies depending on what type of prey was consumed by the hawk, and the size and frequency of casts being regurgitated differs from species to species. While owls can produce one to three pellets a day, hawks may do so less frequently, from one every day to one to two per week.
Through the curiosity inspired by our Red-Tailed Hawk, I have learned so much about something I never considered before. From now on, every time I feed the birds I will be on the lookout for a seldom seen hawk pellet from Cheyenne!