1) Since I've had such interesting feedback (all from expert birders whom I greatly respect) following
my last post on this topic, I would like to respond to some of that feedback. Those of you who wrote to me expressed VERY
different opinions. Some think all data should go to the National Audubon Society (NAS) - I am inclined to agree with that
view. Others think we should avoid the hassle and just send the data to WSO only. If there is a choice between doing that
and not doing a CBC, I would agree. However, I hope it does not come down to that for the majority of participants.
The reasons for sending all data to NAS boil down to an important one: to make the most of the data
for conservation and research purposes, it should go to one national respository. If a researcher wishes to thoroughly study
the winter bird population data for a species, he or she would need to access it from dozens of state organizations' publications
and/or websites. That is extremely complicated, expensive, and time-consuming. Ideally, if all data went to NAS, it would
simplify matters considerably. Unfortunately, things are not that simple - as least as things currently stand.
2) Although the CBCs are our best range-wide source of information regarding early-winter bird populations,
numerous analyses of CBC methodology and data reveal bias of various types. They include the following:
a) Varying levels of observer skill
b) Use of “attractants” (owl tapes; “pishing”, etc.)
c) Varying methods of counting birds at feeders
d) A focus on counting at areas of concentration
e) Changing the count date
f) Changing the count center
g) Changes in use of different types of transportation, because all data is pooled, regardless of
how it is obtained
h) Changes in weather conditions
-Eliminating at least some of these sources of bias can be accomplished. Providing identification
workshops for beginning birders helps with (a).
-Keeping track of what methods are used, and controlling which methods are chosen, may help in the
case of (b).
-Choosing only one method to count at feeders helps to eliminate (c).
-Try NOT focusing on areas of concentration - not as easy as it seems (d).
-Unless it becomes absolutely necessary, never make major changes in the date (or relative date within
the count period), and never change the count center - that takes care of (e) and (f).
-(g) will be quite complicated, but methods exist for dealing with data gathered by varying means
of transportation (but that's too complicated to go into, here).
-Finally, we really have no control over the weather! If we keep the count date the same, some years
the weather will be mild, and other years very harsh.
3) How can we improve our own CBCs? Here are a few suggestions:
a) Set up permanent counting territories, and keep data from these separately.
b) Careful mapping of count territories
c) Mapping individuals of some species for intensive study (GPS use, GIS, etc.)
The last two to list were already mentioned, but they bear repeating:
d) Training sessions for new participants
e) Send all CBC data to NAS.
See much more, with additional detailed discussion (by Sam Droege), with his list of suggestions
and explanations, found at the USGS Patuxent Wildlife Research Center's "Manager's Monitoring Guide", at: http://www.pwrc.usgs.gov/monmanual/
Undoubtedly, not everyone will agree with these suggestions. I submit them for your consideration,
and to hopefully inspire further dialogue.
