Evaluation of aerial surveys of ptarmigan (Lagopus spp.)

• Main Author: Pelletier, Luc
• Format: Thesis
• Language: English
• Published: 1996
• Subjects: Arctic; Yukon
• Online Access: http://hdl.handle.net/2429/4711

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. Science, Faculty of Zoology, Department of Graduate