Annual Precipitation and Bird Population
Caitlin Gorden, Jamie Jefferson, James Nooyen Jr.
University of Wisconsin-Platteville
Introduction
• The Christmas Bird Count started on Christmas day in
1900 to prevent widespread shooting of birds, and
promote simply counting them. The dataset goes back to
1900 and it evolved into a countrywide movement.
• One count made within a predetermined 15 mile
diameter area over one day. All counts take place
between December 14th and January 5th.
• Counts rely on volunteers to contribute data, so some
error must be taken into account regarding volunteer
effort.
• Data collected each year by the CBC has been used by
a number of researchers for their publications. Their
findings have been used to spur conservation efforts,
track long term health of birds, and follow migration
patterns.
• Riveredge Nature Center, located in Saukville,
Wisconsin, has been collecting data for the CBC since
1969.
• With these data sources, we checked to see if there was
a correlation between precipitation levels and
populations of select finch species, specifically the
Purple Finch (Carpodacus purpureus), Pine Siskin
(Carduelis pinus), and American Goldfinch (Spinus
tristis).
• We hypothesize that there will be a significant correlation
between yearly precipitation levels and population sizes
of C. purpureus, C. pinus, and S. tristis within the dataset
provided by the Saukville Riveredge Nature Center from
1969-2011.
Birds Used:
• There was no significant correlation found between
precipitation levels and populations of specific finch
species in the Saukville area.
Purple Finch (C. purpureus)
Pine Siskin(C. pinus)
American Goldfinch (S. tristis )
• We used these species because they are in the same family and
have data all the way back to the beginning of the count. They also
fluctuate from year to year, providing a window to determine if the
fluctuations are correlated with precipitation. They eat mainly seeds
with weeds, berries, and sometimes insects as supplements, which
are affected by precipitation.
• Annual precipitation data was taken from the NOAA Data Climatic
Data Center for Port Washington, WI as it is the closest data
collection center to the Riveredge Nature Center.
• To standardize the bird count data, we adjusted for volunteer effort
(birds per party hour= total number of birds seen/ total number of
party hours in the field). Then a regressional analysis was run using
Microsoft Excel to linearize the correlation between the selected
finch populations and annual precipitation in order to determine if
there is a positive or negative relationship between the two
variables.
Results
r2-value
• The lack of a significant correlation could be due to other
factors or a combination of factors affecting finch
population sizes.
• Link, Sauer, and Niven used CBC data in combination
with weather data to look at population changes of
Northern Bobwhites from 1964 to 2004. (Link, Sauer &
Niven, 2011)
• Root found that precipitation is frequently associated
with the range limits of bark gleaners and seed eaters on
a continent-wide scale. (Root , 1988)
• The same methodologies can be applied to test other
possible correlations between precipitation levels and
other bird species.
• This could also be used to correlate specific bird species
to other bird species, i.e. hawk to finch populations, etc.
References
C. purpureus
C. pinus
S. tristis
0.00608
0.00201
0.06766
History of the christmas bird count. (2013). Retrieved from
http://birds.audubon.org/history-christmas-bird-count
Table 1 – The r2 indicates the correlation strength between annual
precipitation and finch populations.
Fig. 1 – C. purpureus adjusted counts plotted against annual
precipitation (cm). No significant correlation found to exist
between bird population and annual precipitation. Trend line
included. Each point represents one year of data between
1969 and 2011.
Acknowledgements
• We would like to thank all contributors and volunteers of
the Audubon Christmas Bird Count that have spent
numerous hours collecting the data that made this
research possible.
• Thanks to the Riveredge Nature Center for providing
access to their CBC data.
• A special thanks to our professor, Dr. Huebschman, as
well as our class members who took the time to give us
feedback.
Conclusions
Methodology
Fig. 2 – C. pinus adjusted counts plotted against annual
precipitation (cm). No significant correlation found to exist
between bird population and annual precipitation. Trend
line included. Each point represents one year of data
between 1969 and 2011.
Fig. 3 – S. tristis adjusted counts plotted against annual
precipitation (cm). No significant correlation found to exist
between bird population and annual precipitation. Trend line
included. Each point represents one year of data between 1969
and 2011.
Link, W. A., Sauer, J. R., & Niven, D. K. (2011). Combining breeding
bird survey and christmas bird count data to evaluate seasonal
components of population change in northern bobwhite. Journal of
Wildlife Management, 75(8), 44-51. doi:
http://dx.doi.org/10.2193/2007-299
National Oceanic and Atmospheric Administration, National
Environmental Satellite, Data and Information Service. (1969-2011).
Noaa climatological data annual summary wisconsin. Retrieved
from website:
http://www.ncdc.noaa.gov/IPS/cd/cd.html?_page=0&jsessionid=B2
5FC89C7EAF642ED67F6596715FF570&state=WI&_target1=Next
>
Root , T. (1988). Environmental factors associated with avian
distributional boundaries. Journal of Biogeography, 15(3), 489-505.
Retrieved from http://www.jstor.org/stable/2845278