MSS North Owl Use (2)
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University of Washington *
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Geography
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Feb 20, 2024
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Worksheet for reading by North et al. (1999) Your Name: Marisela Sampaga-Smith
1. In your own words, what is the central question North et al. are trying to answer? (hint: see last paragraph of introduction)
What other factors influence local prey abundance in forage site location?
2. In your own words, why do North et al. think this question is important? To determine what other influences may be at hand, the study of the forest structures in some locations relate to the owl-use intensity.
3. North et al. did not state a hypothesis or predictions. What would you say their hypothesis was? (hint: see last paragraph of introduction)
Old-growth stand structure creates or influences future owl habitat.
4. What would you say their predictions were? (hint: see the first paragraph of variable selection section). Due to previous states of stand structure, different levels of foraging use at known spotted owl sites can determine changes in owl-use intensity.
5. This study starts with a baseline knowledge of where owls forage. This knowledge is based on
previous studies, such as the one whose main figure is shown below, where researchers map the owls’ movements over many days, across an area with different forest types. Looking at the figure below, it appears that old growth forest is the most commonly used habitat type for this owl. Make sure you agree with that assessment when you look at the figure. Given that we already know usage rates of different areas, usage rate becomes the independent variable. This seems backward, but for this study it is not. Habitat structure depends on the rate of usage of each habitat. List at least 3 of the dependent variables (habitat structure variables) measured in North et al.? Trees, understory vegetation, and canopy structure were all dependent variables of the habitat.
6. Describe the basic shape, size, and placement of vegetation sampling plots used in North et al.
Large, crown shaped vegetation plots that either contained a small or open diameter with various dimensions of trees in their height and decay class.
7. Related to question 10, how did North et al. decide where to place their plots?
Predominantly old-growth locations, the shape of vegetation revolved around places with water level content and mixture of forest conditions. They made their decision based on geographic range having relative homogeneity throughout.
8. The North et al. study seeks to generalize about the microhabitat preferences of northern spotted owls. What are some flaws in their study design? Hints: a) The study was performed at only 3 sites in Washington. Why is this a problem? B) They say that for the purposes of statistics, the unit of analysis is the number of stands (a stand is a patch of forest) studied, not the
# of owl pairs studied. Why is this a problem? A)
Having only three sample sites in Washington is flawed because the objective is measuring the forage of owls in their habitats where they reside. Perhaps using one or
any consistent number in points of location within the Pacific Northwest could have created more variable matter. B)
This is a flaw because the owls may differ in form, age, and population already in the area(s). If it were to measure or record the owl-use intensity, perhaps the same owl is being conducted rather than the number of pairs that should be observed.
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