[BCNnet] crows & west nile

Wed, 19 Mar 2003 06:35:22 -0600

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With the West Nile virus season about to begin again, and in the news, I =
offer a belated comment on Christmas count numbers of crows. A review of =
the past 10 years of count data was excellent, but missed a longer scale =
factor. During those 10 years crow numbers were much higher than over =
the previous 20 years, judging from a rather cursory scan of Evanston, =
Barrington, Lisle, Chicago Urban & Cal City counts, which verifies my =
personal experience with crow numbers since 1976. Beginning in the 80's =
and accelerating in the 90's, number of crows per party hour increased =
by as much as a factor of 10, from about 1 to 6 per hour to as many as =
30 to 40 per hour. Numbers for this past count were well within the =
range commonly reported during the 70's and much of the 80's. Such a =
dense population is much more susceptible to the spread of an infectious =
disease. There seems to be no similar factor with blue jays and =
chickadees, though, whose count numbers through the 90's were similar to =
those of the previous 2 decades.
A curious quirk in crow data does show up. In several circles, most =
dramatically Barrington and Joliet, there was a huge increase in crow =
numbers in 1976-78, which then dropped off as rapidly. In 1977 crows per =
hour were 32 in Barrington and 43 in Joliet. There was a small spike in =
Chicago Urban, and none in Evanston, Lisle or Cal City. Does anyone =
remember this and have any theories as to why?
John Elliott

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<DIV><FONT size=3D2>With the West Nile virus season about to begin =
again, and in=20
the news, I offer a belated comment on Christmas count numbers of crows. =
A=20
review of the past 10 years of count data was excellent, but missed a =
longer=20
scale factor. During those 10 years crow numbers were much higher than =
over the=20
previous 20 years, judging from a rather cursory scan of Evanston, =
Barrington,=20
Lisle, Chicago Urban &amp; Cal City counts, which verifies my personal=20
experience with crow numbers since 1976. Beginning in the 80's and =
accelerating=20
in the 90's, number of crows per party hour increased by as much as a =
factor of=20
10, from about 1 to 6 per hour to as many as 30 to 40 per hour. Numbers =
for this=20
past count were well within the range commonly reported during the 70's =
and much=20
of the 80's. Such a dense population is much more susceptible to the =
spread of=20
an infectious disease. There seems to be no similar factor with blue =
jays and=20
chickadees, though, whose count numbers through the 90's were similar to =
those=20
of the previous 2 decades.<BR>A curious quirk in crow data does show up. =
In=20
several circles, most dramatically Barrington and Joliet, there was a =
huge=20
increase in crow numbers in 1976-78, which then dropped off as rapidly. =
In 1977=20
crows per hour were 32 in Barrington and 43 in Joliet. There was a small =
spike=20
in Chicago Urban, and none in Evanston, Lisle or Cal City. Does anyone =
remember=20
this and have any theories as to why?</FONT></DIV>
<DIV><FONT size=3D2>John Elliott</FONT></DIV></BODY></HTML>

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