[CT Birds] Bird Species Population Declines

Chris Elphick elphick at sbcglobal.net
Wed Jan 7 13:50:39 EST 2009

Trends for North American species are also available at the USGS's Breeding Bird Survey (BBS) site:  http://www.pwrc.usgs.gov/BBS/ (see the "Results and Analyses" link).  

The best way to do this is to click on "Trend estimates", then on the species of interest.  This will give you a bunch of statistics.  If you then click on the region of interest though, you'll get a graph that shows the actual data for the relevant region.

You can look at continental, regional, or state level trends .... and also get information on how reliable the trends are (they tend to be less reliable at the state level, especially with small states, because the amount of sampling is low).  Trend estimates also tend to be less good for rare species, colonial species, species associated with wetlands, and species that primarily occur in areas with few birders.

Nonetheless, the BBS is by far the best source of information on population trends for most North American species.  Most importantly, the survey uses a standardized protocol and has been running for >40 years.  This means that the year-to-year fluctuations and local variations that are well known to exist in all natural populations can be "dialed out" making it much easier to detect real trends.


Chris Elphick

Storrs, CT

elphick at sbcglobal.net

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