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UBC Theses and Dissertations
Evaluation of aerial surveys of ptarmigan (Lagopus spp.) Pelletier, Luc
Abstract
Ptarmigan (Lagopus spp.) range over most of the Canadian arctic and alpine; thus, a technique is needed to track their densities over a large scale, which current techniques do not. I evaluated a program of aerial surveys done from 1990 to 1996 at Kluane, Yukon, which could do so. The indices of density obtained from aerial counts were subject to many types of errors. Of these, the counting bias, probably the largest source of bias, could have been corrected partially by using the simultaneous 2-sample capture-recapture method. However, the correction factors were highly imprecise due to the low number of double-counts. The variation of total survey bias (with 5 replicates of the survey over 2 weeks in 1996) was low in comparison to the variability of the indices between years; thus, the technique is repeatable. About 70% of the variability of the index in a given year could be attributed to daily factors. I also calibrated the index using ground counts (line transect estimates based on perpendicular distances). A test of accuracy of the linetransect method on a 0.77 km2 grid showed line-transect estimates had low bias (-3 to -7%). The calibration showed a positive and linear relationship between the aerial index and ptarmigan density. However, this calibration held only across areas in the same year. The 1996 index was significantly lower than the 1995 index but the density was higher in 1996. This could be explained by a reduced flushing behaviour in 1996, perhaps caused by increased avian predation pressure. Other indices of abundance of the Kluane ptarmigan population from winter encounter rates are also unreliable as they also predicted a drop in abundance for 1996 while the density actually increased. I recommend the use of line-transects to wildlife managers since the technique provided accurate and fairly precise (%cv = 15-25%) estimates of density.
Item Metadata
Title |
Evaluation of aerial surveys of ptarmigan (Lagopus spp.)
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1996
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Description |
Ptarmigan (Lagopus spp.) range over most of the Canadian arctic and alpine; thus, a
technique is needed to track their densities over a large scale, which current techniques do not. I
evaluated a program of aerial surveys done from 1990 to 1996 at Kluane, Yukon, which could do
so. The indices of density obtained from aerial counts were subject to many types of errors. Of
these, the counting bias, probably the largest source of bias, could have been corrected partially
by using the simultaneous 2-sample capture-recapture method. However, the correction factors
were highly imprecise due to the low number of double-counts. The variation of total survey bias
(with 5 replicates of the survey over 2 weeks in 1996) was low in comparison to the variability of
the indices between years; thus, the technique is repeatable. About 70% of the variability of the
index in a given year could be attributed to daily factors. I also calibrated the index using ground
counts (line transect estimates based on perpendicular distances). A test of accuracy of the linetransect
method on a 0.77 km2 grid showed line-transect estimates had low bias (-3 to -7%). The
calibration showed a positive and linear relationship between the aerial index and ptarmigan
density. However, this calibration held only across areas in the same year. The 1996 index was
significantly lower than the 1995 index but the density was higher in 1996. This could be
explained by a reduced flushing behaviour in 1996, perhaps caused by increased avian predation
pressure. Other indices of abundance of the Kluane ptarmigan population from winter encounter
rates are also unreliable as they also predicted a drop in abundance for 1996 while the density
actually increased. I recommend the use of line-transects to wildlife managers since the technique
provided accurate and fairly precise (%cv = 15-25%) estimates of density.
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Extent |
3537978 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-02-17
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0087246
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1996-11
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.