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Hi Everyone,
It's important to keep these absolute population estimates that have
been thrown around in perspective. The population estimate from the
analysis of Breeding Bird Survey routes is really just an index, a stake
planted at the yearly high tide mark if you like, that can be used to
compare the same survey route done in past years and that will be done
in future years. I'm sure Murray has a much better idea of the real
number of Belted Kingfishers in his area since he birds a much wider
area than the few breeding bird surveys in the southern end of the
province cover. However, the main purpose of the Breeding Bird Survey is
to produce a long term 'population trend'. As I wrote before Christmas,
that trend for Nova Scotia as a whole is given as -4.67%. NOTE: this is
percent change per year, not percent change over 40 years, meaning the
analysis shows a significant decline in the population of Belted
Kingfishers in Nova Scotia over the past 40 years. To put it another
way, the analysis suggests that there are only about one quarter as many
Belted Kingfishers in the province as there were 40 years ago.
For those of you who wish to delve deeper into this subject I suggest
reading the following papers:
Bystrak, D. 1981. The North American Breeding Bird Survey. Pp.
34-41 in C. J. Ralph and J. M. Scott, eds. Estimating numbers
of terrestrial birds. Studies in Avian Biol. No. 6.
Droege, S. 1990. The North American Breeding Bird Survey. Pp. 1-4
in J. R. Sauer and S. Droege, eds. Survey designs and
statistical methods for the estimation of avian population
trends. U.S. Fish Wildl. Serv. Biol. Rep. 90(1).
-----, and J. R. Sauer 1989. North American Breeding Bird
Survey annual summary 1988. U. S. Fish. Wildl. Serv.,
Biol. Rep. 89(13):1-16.
-----, and -----. 1990. North American Breeding Bird
Survey annual summary 1989. U. S. Fish. Wildl. Serv.,
Biol. Rep. 90(8):1-22.
Peterjohn, B. G., and J. R. Sauer. 1993. North American
Breeding Bird Survey annual summary 1990-1991. Bird
Populations 1:1-15.
Robbins, C. S., D. Bystrak, and P. H. Geissler. 1986. The
breeding bird survey: its first fifteen years, 1965-1979.
U.S. Fish Wildl. Serv. Resour. Publ. 157. 196pp.
All the best,
Lance
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