Dienstag, 11. Juni 2013

Bird pellets, part 2

Eagle owl (Bubo bubo).
Hello and welcome to my second and probably last part of my pellet series. If you read my last entry you should know a lot about bird pellets right know, but today I want to share my experience with anatomizing an owl pellet with you. The bones which can found in owl pellets can give you some clues about the food spectrum of that owl. But there’s much more to learn, please continue reading under the cut!

I have several owl pellets around so first I didn’t know which one I should choose. My boyfriend told me to take the fat barn owl pellet, because there could be a lot of bones inside, so I did. But before I started I had to prepare my workplace.
I covered my workplace with a fabric towel and several paper towels. Next to this I need some toothpicks (not visible on the picture), some tweezers and a small colander. I got an old tooth brush ready, too, but I didn’t use it. And don’t forget to wear rubber gloves! I also used a plastic cup and a paper plate.
For to clean my tweezers after work I prepared some Javelle water and hygiene spray.

I got that barn owl pellet from a ranger, so I didn’t know if it was already disinfected. I soaked the pellet in 70% alcohol for ten minutes and after this time I doused it with boiled water. Like you put a bouillon cube into the water the water got brownish and it smelled very, well, interesting... I soaked the fat pellet for about 20 more minutes, then picked it up and placed it on the paper plate.

With two toothpicks I pulled the pellet apart - it’s incredible how furry a pellet can be! The first bone I spotted was a pelvic bone. After this I found a ton of ribs. Sometimes I lost my patience with these tiny ribs and I only took care about the bigger bones. I was so excited when I discovered the first skull!

I moved all found bones to one side of the paper plate. When I finished my work with the pellet, I took the bones into the colander and rinse it under flowing tap water. That’s a good way to get rid of the fur which still stucks to the bones. But it’s impossible to get rid of all the hair as in the braincase of a skull there’s usually a lot of hair left. But whatever, I layed out the bones on paper towels for drying.
If you are finished with your pellet, clean your workplace very well, especially if you work in the kitchen! The fur, plastic cup and these things I throw in the household garbage.

In the end I found three mice skulls, six pelvic bones and also six lower jaw bones in the pellet. And of course a lot of other tiny bones. And ribs… It seems that the barn owl had a rich meal. Let’s have a look at the teeth. I don’t know how to say it in English, but the teeth don’t have roots like human teeth. That’s typically for voles!
Too bad that all skulls were damaged, so it isn’t easy to figure out what kind of vole they were. If you have a microscope and a book about mice skulls you can possible identify them. For my German readers I highly recommend this book!

You can find it here.
If you are able do identify the species of mice within owl pellets you will know what kind of small mammals live in the area. But what’s about the owl which created the pellet? What kind of owl was it?
First evidence is the location where you found the pellet. But a lot of owls live in woods, so what now? The size of an owl pellet is the second evidence. An eagle owl can create a 10cm long pellet which a cross-section of about 4cm. On the other hand a long-eared owl creates only small pellets of about 4cm length and 2cm cross-section dimension. But the size of a pellet depends of how much an owl ate.
The third evidence is the color and the shape of the pellet. The pellets of barn owls are often black and bulgy. The pellets of tawny owls are often bulgy, too, but the color is more greyish.
Sometimes the content of the pellet is an evident, too. Pygmy owls and little owls love to eat insects, so their pellets will contain a lot of chitin parts.

So, we are at the end of my second bird pellet entry. I hope you enjoyed it and maybe you feel like going out into the wood, looking for owl pellets. Even you find none of them, it will be fun. Keep hunting!

4 Kommentare:

  1. >but the teeth don’t have roots like human teeth. That’s typically for voles!

    Actually, it's a bit more complicated: molars from the bank vole (Myodes glareolus) has roots like human teeth, but the molars from the field vole (Microtus agrestis) and water vole (Arvicola terrestris) go straight down without any roots.

    And thanks for the book tip. You wouldn't by any chance know of any German book that deals with the postcranial skeleton of small mammals? There are several skull guides in various languages, but I haven't seen many that discuss the other bones.

    1. Actually I wanted to say "schmelzfaltig" but I didn't find any translation for that word. It means the shape of the teeth of voles. So I talked about the root-thing. But thank you :)

      In that red booklet are mostly skulls, sorry. Neither I don't know another book of small mammal bones.

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