UBC Theses and Dissertations
Effects of band-tailed pigeon behavior on estimates of population parameters Kautz, Jerry Edward
During the summers of 1973 and 1974 a study was conducted in the Rio Grande Valley of Colorado to determine whether trap samples of bandtailed pigeons (Columba fasciata) are randomly drawn from the population. Counts and trap samples at the same site and time of day did not give significantly different estimates (P>0.05) of tagged proportion or immature proportion. Therefore, counts were representative of trap samples. Analysis of count data indicated that trapping would sample the population feeding at a site randomly with respect to tagged proportion, but not with respect to immature proportion. Immature proportions differed significantly (P<0.05) at different times of day at many feeding sites, at different times of year at the same feeding site, and at different feeding sites at the same time of year. Tagged proportions in counts decreased with distance from the tagging site, but the decrease was not uniform from site to site and appeared to depend upon flight patterns of bandtails. Frequency distributions of distance between captures of pigeons caught twice in Colorado were significantly different (P<0.001) for immatures and adults and for adult males and females. Immatures dispersed long distances more often than adults and adult males had a smaller feeding range than females. The frequency distribution of recapture distances for adult pigeons banded and recaptured in the same year was significantly different (P<0.001) than that for adults banded and recaptured in different years. Tagged proportions in hunter kill samples and count samples did not differ significantly (P>0.05), but immature proportions did differ significantly (P<0.05). It is concluded that capture-recapture methods can be used to calculate an index of population size, but care must be used in selection of trap sites and in interpretation of population data. Trap data and hunter kill data should not be used to estimate immature proportions.
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