Lynnwood Elementary Ornithologists Study Owls

Today Lynnwood 4th grade ornithologist studied owl with me. Four classes dissected owl pellets and found the following.

Mrs. Janssen’s class dissected 11 pellets and found 31 mice, 1 shrew, 0 moles, 0 birds
Mrs. Lodge’s class dissected 9 pellets and found 21 mice, 2 shrew, 0 moles, 0 birds
Mrs. Shields’ class dissected 11 pellets and found 30 mice, 1 shrew, 1 moles, 0 birds
Mr. Freeman’s class dissected 10 pellets and found 29 mice, 1 shrew, 0 moles, 0 birds

All four fourth grades combined dissected 41 pellets and found 111 mice, 5 shrew, 1 mole and 0 birds. Do these numbers support the hypothesis that was discussed in class?

During one class our discussion touched on how many animals does an owl eat for a meal. For this we need to look at our data and calculate an average. Now for most 4th graders this will be a new mathematical computation. To get an average, of course, we need to total the number of animals found in the pellets, 117, and divide it by the number of pellets dissected, 41. The average for our data therefore is 2.9, almost 3 animals per meal. Compare this average to the averages for owl pellet dissections done by other classes (see - Ostrander Elementary on March 8, 9 and 10; Jefferson Elementary on February 3; Nazareth Intermediate School on January 25, 26 and 28; and Circleville Elementary on November 4, 2009 - there are other investigation recorded on dates previous to these that you can search for in the blog). You will find that this is a little higher. Why might this be? Remember, ever scientist starts their science work with a question.

There might be a couple of reasons why. One might be a result of the start of the spring season. The owl pellets that were dissected were collected soon after they were produced by wild owls. That means these pellets show what the owls are eating now, in the early spring. The mice in northern California, Oregon and Washington, where these pellets come from have already started there reproductive cycles. Owls would hear the sounds and activity of a mouse nest, land on the nest and eat up the mouse family all at once. Indeed, there were several pellets dissected that had 5 or 6 mice in them, with all of the skulls being quite small. This would support this hypothesis, since the small skulls would be from young mice.

Another possibility is that the pellets dissected were not an average sample of owl pellets. Since I order many pellets from Pellets Inc. and I had to pay extra for a rush order to get these in time for our study, the sales representative told me he would make sure we had large pellets. Large pellets usually might occur when an owl eats a larger than usual meal. If he was carefully picking large pellets for our order that might result in a larger average of animals per pellet change our findings.