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There is a chance you might have dissected an owl’s pellet in school science class or in a nature center, at a certain point in life. If you have never done so or don’t know what they are, we will help you find out.
Here, we will go over what owl pellets are, where they come from, their use, and other related questions.
As the name suggests, owl pellets are regurgitated parts of the owls’ prey. Like most birds, owls do not chew their food, so they have to swallow it whole. However, they differ from other birds since they do not have a crop.
A crop is a baglike organ of the digestive tract which helps birds store food before breaking it down in the digestion process. Owls lack a crop, which means food goes directly from the mouth to the gizzard.
The gizzard is part of the digestive system that is like a stomach. It contains small stones and sand, which help with digestion. It also has muscular ridges with which it grinds food.
The food gets digested by the digestive fluids, and usable tissues get dissolved. This tissue contains vital substances like proteins, fats, and so on. They include fat, skin, muscle, and internal organs from the prey.
Other substances such as bones, feathers, and fur do not get digested. Instead, they get compacted by the gizzard into a thick paste-like pellet. After that, they pass into an owl’s digestive structure where they eventually get excreted.
This white thick paste-like excrement is referred to as urea and is rich in nitrogen. Although the owl pellets resemble scat, they are not poop.
The indigestible material such as skulls, teeth, feathers, and claws are too dangerous to pass through the intestines. They could cause a blockage or damage. To safely excrete indigestible parts, the owl’s gizzard compacts them into a pellet. The pellets get regurgitated from the mouth in a special kind of casting which takes several minutes to complete.
Owl pellets can be useful for research purposes. They are used to gather information on the food owls eat and studying their feeding habits. They can give insight into an owl’s diet as well as the local prey and environment.
These pellets can also give information on diseases and parasites owls carry. Additionally, most of the prey’s bones survive both the attack and the subsequent digestive process.
That makes it easy to identify them in the pellet. That way, researchers can easily identify the prey by simply looking at the skulls. If the owl consumes several animals in a short period, the pellet will contain all their bones at once.
Generally, large owls like the European Eagle Owls (Bubo bubo) can produce large pellets that weigh more than an ounce. However, large owls do not always feed on large prey, and you can’t always tell the size of the owl by looking at the size of a given pellet. Also, startled owls may regurgitate pellets without compacting them, and they end up seeming larger than usual.
This process of regurgitating pellets is not unique to owls only. Other raptors like hawks, falcons, and eagles can do the same. However, they produce smaller pellets that contain fewer bones and other animal parts.
Storing and regurgitating pellets is a great adaptation that helps owls safely expel indigestible materials. Now that you know what owl pellets are, how are they stored?
The formation of a complete owl pellet takes a few hours after ingestion. It is not, however, ejected immediately after getting formed. Instead, owls store them.
To store them for several hours, owls have a small structure called proventriculus that holds the pellets. Here these pellets can stay for as long as twenty hours before disgorging.
It’s also good to note that the stored pellet blocks the entrance of the rest of the digestive system. To eat again, owls must regurgitate the stored pellet. Keep in mind young owls do not regurgitate pellets.
The process of regurgitating pellets is very similar to that of vomiting. First, owls contract their esophagus muscles to push the content out. Second, they pull their head back, open the bill and let the pellet fall out.
The process makes it seem as if the owl is coughing and in great pain. That is not usually the case since the pellets remain moist and soft until they leave the mouth. It also takes a few seconds or a few minutes.
The texture and shape of any given owl’s pellet will depend on several factors. The most important factors are the type of prey (bird, rodent) and the type of species of the owl. Different owls have different-shaped pellets since they don’t feed on the same food.
Some owl pellets are furry, oval, and tightly compacted. Others are large, loose, and irregular in shape.
Although they are usually moist at first, they quickly dry out and start decomposing. To find some, you can look near barns and under trees. These are typical places where owls perch.
They are mainly cylindrical in shape, dark in color – from light gray to black and medium-sized. The pellets can be an inch long and half an inch wide. For instance, tiny Elf Owls produce owl pellets that are very small, loosely compacted, and dry.
The main reason for that is because of their insect diet. On the other hand, the Great Horned Owls produce large cylindrical pellets. These pellets are usually tightly packed and could measure about 3-4 inches long.
That’s because they feed on rodents, small mammals, and large prey like skunks or opossums. The outside appearance of the pellets may vary due to the many animals that Great Horned Owls feed. Additionally, the number of these pellets an owl will produce after eating depends on the size and number of the prey.
If you are curious to know what items are in the pellets, you can dissect them and find out. The process is relatively simple, and it allows you to investigate what owls eat.
Before dissecting an owl’s pellet, you can soak it in warm water to make it softer. You can also break in half and gently pull apart pieces of the content.
After finishing, sort all of the items by prey by size and type and record them in a notebook. If you’re a student or a researcher, you can easily reconstruct the bones using a bone identification chart. That way, you will be able to sort and compartmentalize the skeleton and hopefully identify the prey.
Keep in mind that not all will get identified since owls swallow lots of different animals. That said, a few things you might find include teeth and bones from rodents. Owls like Barn Owls feed on mice and voles.
A loosely compacted pellet from an elf or flammulated owl will contain exoskeleton bits. That’s because this type of owl feeds on insects like grasshoppers and crickets.
When it comes to the Great Horned Owls, the pellet will contain diverse bones from different animals. The main prey is usually rabbits, skunks, or woodchucks, but they also eat mice and voles. You might also find feathers, beaks, and talons from other birds. That’s because they also feed on smaller birds like doves, grouse, and sparrows.
You can also find decapitated heads and torn-off wings of birds scattered near the pellet deposits. That’s not strange since this powerful raptor has the most diverse diet than any other bird of prey in entire North America.
It is also worth mentioning that you need to take safety precautions when handling owl pellets. The reason for this is that they may still have some bacteria or parasites. Owl pellets support a whole ecosystem of microorganisms from fungi to carpet beetle larvae.
So, it’s advisable to sterilize your hands before and after touching them as recommended by the US CDC. Also, ensure you have disposable gloves and lab safety goggles when dissecting them.
Additionally, you can have all other tools and containers, as listed at BirdsCornel.
To know more about dissecting procedures, check out the Barn Owl Pellet analysis worksheet.
In a nutshell, owl pellets are a good source of information for what birds eat. They can also be an educational tool to show students bones organized in animals.
However, it’s critical to be careful when dissecting them and make sure you take all safety precautions. If you don’t, there is a chance that some bacteria and parasites could affect you.
Next time you see a pile of owl pellets outside, you know what they are and what to do. With this said, it’s up to you to decide whether to dissect them or not. Just keep in mind that you need to know how to approach the situation and the risk involved.
Robert’s obsession with all things optical started early in life, when his optician father would bring home prototypes for Robert to play with. Nowadays, Robert is dedicated to helping others find the right optics for their needs. His hobbies include astronomy, astrophysics, and model building. Originally from Newark, NJ, he resides in Santa Fe, New Mexico, where the nighttime skies are filled with glittering stars.
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