THE RELIABILITY OF ESTIMATES OF DENSITY FROM TRANSECT COUNTS
| Posted: |
25/09/2021 |
| Author(s): |
H. L. Bell, S. Ferrier |
Densities were estimated from transect counts for seven species at Wollomombi,
New South Wales. These estimates are compared with accurate densities derived from
intensive studies of colour-banded birds. Also estimates of density of the Golden-headed
Cisticola
Cisticola exilis, at Port Moresby, Papua New Guinea, are compared with seasonal
changes in behaviour of that species. Three methods of analysis were applied to the
transect data: the Fixed-strip Transect. Variable-strip Transect and the Line Transect
Methods. While all methods tended to underestimate density the Variable-strip and Line
Transect Methods performed much better than the Fixed-strip Transect Method, because
they attempted to overcome problems associated with varying detectability. However, the
bias of estimates was not constant and differed greatly between species and between
seasons. These results demonstrate the need for caution in using transect methods to
compare densities where the detectability of birds may differ. It is concluded that no
one method of censusing is appropriate to all species under all conditions and that
combinations of different methods are required for accurate estimates.
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