Wild Memories Photography Tours

Raptors are birds of prey that include eagles, hawks, falcons, kites, vultures, and owls. Although the former five are not closely related to owls they all have one thing in common, they regurgitate their “leftovers.” By leftovers I mean the indigestible parts of the animals they eat like bones, fur and feathers. They could just excrete them along with other wastes but there is a real advantage to the way the get rid of things like bones. To be able to fly birds have evolved a variety of ways to reduce their weight such as hollow bones and getting rid of the indigestible part of their prey as quickly as possible. I never have understood how they so efficiently separate the bones and feathers or fur from the digestible parts of an animal but they do. I have dissected lots of owl pellet over the last 40 years of teaching biology. I have never found anything digestible in those hundreds of pellets.

Raptors such as great horned owls and bald eagles regurgitate a pellet about every 24 hours. The reason I had students dissect owl pellets was so they could determine what they had eaten in the last 24 hours, how many calories they ate, and thus how many calories it took to keep the owl alive. If an owl eats a 300 calorie rat, we know it would take between 3,000 and 30,000 calories of seeds, etc. to raise the rat to “owl eating” size and somewhere between 30,000 and 3,000,000 calories of sunlight to grow the seeds. Owls and eagles are at the top of the food chain. One of the reasons there aren’t as many of them as there are rats is that it takes a lot more calories to keep an owl alive as it does a rat.

The bald eagle pellet came from beneath an eagle roost just south of Yankee Jim Canyon. I think it is the pieces of a grouse. There was no fur in the pellet and all of the feathers look like grouse feathers.

As I write this I can look out the window and see a bald eagle on the top of a pine tree across the Yellowstone River. I don’t know if it is the same eagle that made the pellet but it could be. We are only about 2 miles south of Yankee Jim Canyon.

The great horned owl pellet came from the ground under an electrical pole several miles north of Yankee Jim Canyon. We see a great horned owl sitting there frequently.

This great horned owl pellet is unusual because it contains the remains of at least four rodents.

Look at the lower jaw bones on the right side of the photo below and you will see how I know that. The incisors in between the jaws are from the jaw bone right below each incisor. When the rodent was alive almost all of each of those incisors were inside the lower jaw bone in the process of growing out to add to the rodents worn incisors.

The number of calories of sunlight it takes to keep an owl alive for 24 hours should give you an idea of how many calories you need. This should give you some idea of how humans are having such a huge impact on our earth. We are at the top of the food chain, but our numbers are more like we were rats or some other animal lower on the food chain.
If you want to find your own pellets look under the places you see hawks, owls, eagles, etc. roosting. They are much easier to find in areas with very few trees. They are just like opening a Christmas present because you never know what you are going to find.

Our photos are available at www.vernelehmberg.com. Watch for an upcoming sale soon.