[at-l] B-Owl Movement. Re: Feeling Like Spring

Felix J AThiker at smithville.net
Tue Mar 8 06:46:25 CST 2011


On 3/7/2011 10:48 AM, RockDancer wrote:
>
> Hi all,
>
> I’ve had a great time in past 2 weeks reconstructing the 
> contents of owl pellets that I collected in the local 
> state forest.  There is probably more I could learn but 
> without any training I could sort the mess-o-bones out 
> this way.
>
> *Site 1 – Northern Saw-whet Owl eating White-footed Mice*
>
> Early on I thought this site had either a Northern 
> Saw-whet Owl or an Eastern Screech Owl. This is based on 
> pellet size and the dense white pines where they were 
> found. The 5 pellets contained 5 animals but only 4 
> skulls. From the dental records and skull size they are 
> all genus Peromyscus mice. In my area we have only the 
> White-footed mouse and the American Deer mouse. From the 
> size of the pellet the bird is narrowed down to only the 
> Northern Saw-whet Owl. Now I’d like to see it.
>
> Saw whet owls will kill as many as 6 mice in succession 
> and them in Winter pantries. Later they will brood on the 
> mouse-icle to thaw for eating. If food is plentiful they 
> will eat only the heads. Deer mice is the primary prey and 
> the pellet length is .75 inches.
>
> Screech owls produce 2-4 pellets each day and pellet 
> length is 1.5 inches long. In the winter they will hunt 
> open ice holes left by fishers. We have fishers and river 
> otters in the woods at this location.
>
> *Site 2 - Great-horned Owl eating Meadow Voles and a Grey 
> Squirrel*
>
> I saw the bird and the pellets are from the base of the 
> nest tree, the nest about 90 feet up in a conifer. The 2 
> pellets I collected were a surprise because they contained 
> partial skeletons, and the skeletons were perfectly 
> complementary. This means the bird emptied it’s stomach in 
> 2 “surges” and all the bones were in the stomach at the 
> same time. Taken together I had 5 skulls, 10 pair of lower 
> jaws, 10 pair of leg bones meeting in ball-socket joints 
> (like our hip-femur). All 5 animals are Meadow Voles. We 
> have 3 voles in this area but the skull size determines 
> them to be Meadow Voles.
>
> But the pellets also contained a mystery. An intact chest 
> bone, a larger ball-socket joint (5x larger than a vole), 
> 5 odd shaped vertebrae too large for vole and many flat 
> flexible fragments of what I assume is the skull cap. So 
> this owl also ate something much larger than a vole (which 
> in this case is larger than the mice). Candidates are 
> Flying Squirrel, Red Squirrel, Grey Squirrel, rabbits, 
> skunk, opossum, etc. Based on population I’ll be content 
> to call it a Grey Squirrel. It’s body is 2.5x the length 
> of a Meadow Vole, not quite the 5x increase in size 
> indicated. But then I don’t know how these things scale 
> up. Perhaps the hip joint scales at 2x the rate for the 
> length of body?
>
> That’s all I’ve got for this project. After cleaning and 
> sorting the bones I used the kitchen microwave to 
> sterilize all I had, tossed the rest. This allowed me to 
> handle the bones without worries. Turns out you can get 
> some enteric bacteria from doing this so be careful out there!
>


I'm pretty sure I don't know another person who could have 
made this post. I love you, and your owl pellets, 
RockDancer  :)

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