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.
