Article From SubmitYOURArticle.com: What do Owls Eat for Dinner?

I have been a keen ornithologist for many years
and owls have always fascinated me, especially
the local barn owl which I watched hunting over
nearby farmland on summer evenings. But I always
wondered what they were catching for dinner.

Eventually I tracked the owl to its daytime roost
- a deserted cow shed in the middle of a field.
As I approached the derelict building, the barn
owl flew silently away. I pushed open the rusty
metal door and looked around. Lying on the floor
beneath the roof beams were large, shiny black
bundles of fur, about the size of my thumb. I
picked one up and broke it open to find an
incredible array of small bones, teeth, and two
tiny animal skulls. This was my first glimpse
into what gradually became a major interest, and
I have collected and examined hundreds of owl
pellets from many species of owls over the years.

So what exactly is an owl pellet? It's the
undigested remains of the bird's previous meals.
An owl does not rip the meat off its victims, as
a buzzard or eagle does. Nor does it chew its
food. Instead, it swallows its victims - mainly
small mammals - whole. Once the food is
swallowed, it passes into the gizzard, where the
food is broken up, and then to the stomach for
digestion. Some of the harder parts of the prey
are not (or only partly) digested. These solid
remains are prevented from passing any further
down the gut. Instead, they are squeezed in the
gizzard into a compact mass. This is then coughed
up, or regurgitated as a pellet.

As pellets do not pass through the intestine,
they are quite different from droppings. They do
not smell, and are not unpleasant to work with.
They consist of bones, teeth, claws, beaks,
insect wing cases, frog skins, seed husks etc.
These are enclosed by softer material like fur
and feathers.

Studying owl pellets is extremely worthwhile
because, with a bit of detective work, you can
find valuable information about the diet of the
owl. The solid remains can easily be extracted
and identified. Most species of small mammals are
easy to identify by their skulls and jawbones. It
is therefore possible to identify precisely what
the bird has been feeding on, which provides key
information about the numbers of prey in that
area, the food chains and the precise part the
owl plays in them. Without studying owl pellets,
this information would otherwise be very
difficult to discover.

Dissecting an owl pellet is an easy process. It
is advisable to use surgical gloves at all times.
These can be obtained from your local pharmacy.
Pellets can be teased apart when they are dry,
but it is best to soak them first. Half fill a
bowl with water and a drop of liquid
disinfectant, and leave the pellets to soak for
half an hour. Then take each one out and tease
the pellet apart carefully using tweezers and
cocktail sticks. As you come across bones, pick
them out and lay them on kitchen paper. They will
soon dry, after which they can be identified.

The most distinctive bone of a small mammal, and
hence the easiest to identify, is the skull,
followed by the lower jaws. There are four ways
in which a skull or jaw can be identified: the
actual size of the skull; the dental formula;
teeth cusp patterns; and root patterns.

There are many books available showing clear
illustrations of these four elements of a small
animal's skull. You can also email me for a
simple guide to the identification of skulls and
jaws found in owl pellets.

The first study I conducted on my local barn owls
threw up some interesting data. From the 138
pellets I analyzed over that summer, I discovered
that the owl had eaten 481 prey items. These were
277 field voles, 119 common shrews, 41 wood mice,
22 pygmy shrews, 14 bank voles, 3 brown rats and
3 birds. In other words, in percentage terms, the
owl's preferences were for field voles (58%) and
common shrews (25%).

Contrast this data with an analysis I conducted
of pellets of the tawny owl, which seems to eat a
greater variety of prey items: bank voles (31%),
wood mice (29%), common shrews (21%) and beetles
(10%) forming the bulk of its diet. At the other
extreme is the short-eared owl. A study I
completed on this owl revealed that over 92% of
its diet was composed of field voles.

These statistics reflect the different habitats
of these three species of owl. The barn owl
generally confines itself to open fields - the
domain of field voles - but also hunts alongside
hedgerows and canal banks, where shrews can be
found. The tawny owl's hunting area is generally
woodland, a rich habitat for all kinds of small
animals, but also extends into parks and gardens,
hence its very diverse diet. The short-eared owl
is very much a bird of the upland moors; a harsh
environment where only the field vole can breed
successfully.

Analyzing owl pellets is a fun, harmless
occupation for young and old, and it leads to
simple but fascinating insights into the diet of
these creatures of the night.

----------------------------------------------------
Denzil Walton is a freelance technical copywriter
by profession, but his hobby is nature study. He
has been writing about nature and the environment
since a teenager. Contact him at
http://www.denzil.be for the guide to the
identification of small mammals that he mentions
in this article.

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