Michael D. Hanan
September 2009
Population estimates are important for managers and biologists to make informed
decisions. Wildlife statistics have
focused on estimates derived from counts and population sizes at sample sites by
estimating the proportion of animals counted.
One widely used methodology for sampling avian populations across North
America is the United States Department of Interior Fish and Wildlife Service’s
Breeding Bird Survey. Reliability
of the Breeding Bird Survey data has been criticized due to surveys being
conducted on road transects. The
objective of this project was to assess land cover change in relation to roads
on a landscape level over a thirty year period and relate the results to the
reliability of the Breeding Bird Survey data.
I used land cover at an ecoregion level to assess changes in land cover
in proximity to roads. Ecoregions
provide useful strata in this project because they relate to the environmental
characteristics that derive factors that affect changes in land cover and
wildlife populations. My results showed
little evidence that land cover change correlates with proximity to roads.
Local land attributes can have cumulative effects on bird populations.
I recommend that further research be conducted in respect to off-road
point counts adjacent to BBS routes to detect discrepancies between estimates on
and off-road because land cover at the landscape level does not reveal all
components that affect population trends.
I also recommend that further research be conducted to relate local land
cover change to the landscape approach of this study.
In addition, I highlight priority areas of concern for future research in
respect to the Breeding Bird Survey.